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V  2 


The  Photographic  Image. 


A 

THEORETICAL  AND  PRACTICAL  TREATISE 

OF  THE 

DEVELOPMENT 

IN  THE 

Gelatine,  Collodion,  Ferrotype  and  Silver  Bromide 
Paper  Processes 

BY 

p.  C.  DUCHOCHOIS,  Photographer. 

The  development  is  in  reality  an  art  and  a 
science  combined  :  the  Art  consists  in  getting 
gradation,  the  Science  in  making  your  solu- 
tions to  obtain  it. 

Captain  W.  de  W.  Abney. 


Copyrighted  by  P.  C.  Duchochois,  1891. 


New  York: 
Press  of  WILLIAM  R.  JENKINS, 
851  &  853  Sixth  Avenue. 


1891. 


PREFACE. 


We  have  endeavored  to  give  in  this  work  all 
the  theoretical  and  practical  instructions  neces- 
sary to  guide  one  in  the  operation  of  developing 
the  photographic  image,  and  we  have  described 
the  processes  employed  to  finish  the  cliches  which 
is  the  complement  of  the  operation. 

We  were  led  to  write  it  for  the  reason  that  in 
the  text-books  published  since  a  few  years  the 
development,  although  well  described,  is  not 
treated,  we  think,  with  the  importance  it  merits. 
It  does  not  suffice  to  give  formulas  and  to  explain 
their  use  in  some  cases,  their  applications  should 
be  illustrated  by  examples,  from  those  examples 
simple  rules  should  be  deducted  and  the  special 
action  of  each  of  the  chemicals  employed  must 
be  pointed  out  in  order  that  one  understands 


PREFACE. 


the  results  to  which  give  rise  the  modifications 
made  in  the  constitution  of  the  developing 
solution. 

Not  too  many  instructions  can  be  given,  for  the 
development  is  the  most  difficult  operation  of 
photography,  the  value  of  the  negative  cliches 
and,  as  a  consequence,  the  perfection  of  the 
pictures  depending  from  the  manner  the  latent 
image  has  been  developed. 

Indeed,  it  is  among  many  amateurs  and  even 
professional  photographers  a  common  error  to 
think  that  it  can  be  done  in  a  sort  of  mechanical 
or  automatic  way  as  it  has  sometimes  been 
presented.  There  are  probably  not  two  subjects 
which  can  be  well  photographed  by  operating 
exactly  in  the  same  manner;  and,  to  meet  the 
various  cases  which  present  themselves,  not  only 
should  the  operator  have  studied  the  relation  of 
the  exposure-time  to  the  lighting,  or  oppositions 
of  lights  and  shades,  and  that  of  the  development 
to  the  lighting,  but,  to  the  latter  end,  have  a 
perfect  knowledge  of  the  action  of  the  chemicals 
constituting  the  developing  solution  on  the  parts 
of  the  photo  film  impressed  by  light. 


PREFACE 


Therefore  we  have  written  a  purely  theoretical 
chapter  on  the  behavior  of  the  chemicals  em- 
ployed, which  we  consider  as  a  very  important 
one  and  of  which  we  recommend  the  lecture 
even  to  those  having  no  notion  of  chemistry  : 
for  the  theory  is  the  base  of  practice — it  explains 
the  phenomena,  it  guides  the  operator ;  without 
knowing  the  principles  one  may  occasionally 
produce  excellent  works,  but  generally  the 
results  are  imperfect,  and  whenever  one  meets 
with  failures,  he  is  unable  to  trace  them  to  their 
real  cause. 

We  present  this  work  to  those  interested  in  the 
art  of  photography,  trusting  it  will  smooth  the 
path  to  the  beginners  and  be  useful  to  those  who 
desire  not  to  work  in  a  mechanical  manner. 

P.  C.  D. 

New  York,  October,  i8gi. 


CONTENTS. 


INTRODUCTION. 

PAGE 

Action  of  light— Reversal — Solarization — The  relation 

of  the  exposure  to  the  development,   -      -      -  vii 


PART  I. 


Chaptek  I.  Chemistry  and  behaviour  of  the  reagents 
employed  in  the  development.  Salts  of  iron — Pyro- 
gallol  —  Hydroquinone  —  Eikonogen  ~  The  hy- 
drates and  carbonates  of  the  alkali-metals — 
Action  of  the  alkalies  on  the  reagents — Their 
special  action  on  the  photo-film — The  sulphites — 
Their  action  on  the  reduction  of  the  silver  salts 
— The  restrainers— The  accelerators — Summary 
of  the  actions  of  the  chemicals,    -      -      -      -  3 

Chapter  II.    The  dark  room  illuminationf      -      -  50 

Chapter  III.  The  exposure-time.  Influence  of  the 
exposure  on  the  character  of  the  picture— The 
exposure  in  relation  to  the  lighting  —  Normal 
exposure  defined— Example— Table  of  exposure- 
times — Photometers — The  pendulum,  -      -      -  5t 


iv.  CONTENTS. 


PART  II. 

The  Development  in  the  Gelatine  Pkocess. 

Chapter  I.  Generalities  on  the  development.  The 
development  regulated  both  by  the  exposure-time 
and  the  lighting  of  the  subject— Influences  of 
rapid  and  slow  developments— Two  important 
rules — Examples — The  effects  of  rocking — Eval- 
escense— When  to  stop  the  development — Rule  to 
determine  it  —  Local  and  general  intensities — 
Rule  on  which  is  based  the  development,    -      -  69 

Chapter  II.  The  development  with  pyrogallol.  First 
example:  The  development  of  plates  normally 
exposed,  or  nearly  so  —  Second  example :  The 
development  of  plates  under  exposed — Third 
example :  The  development  of  plates  over  exposed 
— Fourth  example:  The  tentative  development — 
The  development  according  to  the  lighting — 
Example  o/— The  development  of  orthochromatic 
plates — Local  development — The  development  of 
cliches  in  line,  83 

Chapter  III.  Summary  of  the  rules  regulating  the 
exposure-time  and  the  development,  -      -      -      -  94 

Chapter  IV.  Fixing.  The  theory  of — Generalities 
—Berkeley's  fixing  bath,  100 

Chapter  V.  Intensification.  The  chemistry  of — 
Generalities — How  to  obtain  various  degrees  of 
intensity — Intensifying  with  silver,    -      -      -  108 


CONTENTS. 


V. 


Chapter  VI.  Reduction  of  intensity.  The  processes 
usually  employed  —  Their  defects  —  Rational 
method  of  reduction — How  to  treat  cliches  too 
intense  in  the  lights,  123 

Chapter  VII.    Causes  of  failures,    .      -      -      -  133 

Chapter  VIII.  The  development  with  hydroquinone. 
Generalities— Formulas  for  various  exposure- 
times— Tentative  development,     .      .      -      .  144 

Chapter  IX.  The  development  with  eikonogen.  Gen- 
eralities—Formulas  for  various  exposure-times,  -  152 

Chapter  X.  The  development  with  ferrous  oxalate. 
Generalities — Examples,  159 

Chapter  XI.  The  development  with  pyrocatechin,  hy- 
droxylamine,  and  jjaramidophenol,      .      -      -  165 


PAET  III. 

The  Development  in  the  Collodion  and  Silver 
Bromide  Printing  Processes. 

Chapter  I.  The  development  in  the  wet  collodion  pro- 
cess. Theory — Generalities — Normal,  strong  and 
weak  developers — Action  of — Developer  for  line- 
works — Re-development — Intensification— Causes 
of  failures,  173 

Chapter  IT.  The  development  in  the  dry  collodion 
process.  Physical  and  chemical  developers — 
Tentative  development— Fixing,   -      -      -       -  190 


vi. 


CONTENTS, 


Chapter  III.  The  development  of  ferrotypes.  Gener- 
alities— Spiller,  Keith,  and  the  writer's  formulas 
— Modifications  to  obtain  good  whites — Sulphuric 
acid  objectionable — Modus  operandi— Fixing,    -  195 

Chapter  IV.  The  development  of  gelatino-bromide 
paper.  Generalities — Development  with  ferrous 
oxalate  and  eikonogen — Causes  of  failures  and 
remedies,  203 

Chapter  V.    Varnishing,  211 


INTRODUCTION. 


When  a  photo-plate  is  exposed  in  the 
camera  obscura  for  a  period  of  a  few  seconds, 
then  treated  by  a  reducing  agent,  the  developer, 
one  obtains  a  negative  cliche  representing  the 
luminous  image  formed  at  the  focus  of  the 
lens.  The  light  has  therefore  impressed  the 
silver  salt,  but  the  impression  is  not  visible 
and  cannot  by  any  known  means  be  detected 
before  the  development. 

"What  is  this  primary  action  of  light  on  the 
silver  haloid :  is  it  purely  physical,  or  one 
causing  a  partial  or  entire  reduction  ?  It  is  an 
open  question. 

Although  experiment  shows  that  the 
ultimate  luminous  action  results  in  a  more  or 
less  complete  dissociation  of  the  constitutive 
elements,  the  successive   changes  occurring 


viii. 


INTRODUCTION. 


during  the  period  of  exposures  in  the  camera^ 
which  give  rise  by  development  to  a  negative, 
then  to  a  positive,  then  to  a  negative,  then 
again  to  the  same  series  of  transformations, 
as  well  as  the  evalescence  of  the  luminous 
impression,  sustain  the  hypothesis  of  a  purely 
physical  action  :  the  silver  haloid  changing  of 
state  by  displacement  of  the  molecular  centers 
and  the  caloris  producing  the  work  necessary 
to  effect  the  chemical  changes  occurring  in  the 
development. 

From  the  behavior  of  light  on  the  silver 
haloids  it  results  that  the  change  goes  on 
increasing  to  a  certain  limit  which,  in  one  way, 
coincides  with  the  maximum  of  action  pro- 
ducing, by  development,  the  greatest  opacity 
of  reduction,  then  as  the  luminous  action 
progresses  the  reversal  commences  and  causes 
a  reduction  which  becomes  less  and  less 
opaque.  This  phenomenon  is  termed  solariza- 
tion.  It  was  first  observed  by  Moser,  of 
Konigsberg. 

The   solarization  is   the   cause   of  many 


INTRODUCTION^. 


defects ;  thus,  the  sky  in  landscape,  for 
example,  is  devoid  of  opacity  in  the  negative 
and,  as  a  consequence,  represented  by  tinted 
whites  in  the  positive.  Furthermore,  if  the 
sky  was  cloudy,  the  clouds  will  not  be  repro- 
duced :  the  half  lights  always  disappear  in  the 
solarized  high  lights  to  which  they  become 
equal  in  intensity. 

There  are  necessarily  various  degrees  of 
solarization,  and  it  is  on  this  account  that  the 
reversal  is  a  phenomenon  useful  in  photog- 
raphy. It  permits  one  to  reproduce  the 
ensemble  of  the  object ;  without  it,  it  would  be 
impossible  to  photograph  any  object  with 
gradation  from  light  to  shade,  for  not  only  the 
less  refrangible  rays  act  with  much  less  energy 
than  the  others,  but  even  the  weak  lights  from 
the  same  ray  does  not,  in  proportion,  impress 
the  photo-film  as  rapidly  as  the  unmitigated 
ray.  In  fact  the  photo-film  is  impressed  by 
the  white  light  reflected  from  the  surface  of 
bodies,  and  the  colored  rays  reflected  by 
the  body  itself.  Hence  the  rule  to  over  expose. 


z. 


INTRODUCTION. 


During  the  period  of  over  exposure  the 
reversal  necessarily  commences  in  the  high 
lights,  that  is  on  the  parts  of  the  photo-film 
upon  which  are  projected  the  most  luminous 
rays  of  the  object,  while,  the  action  progressing 
on  those  which  correspond  to  the  half  lights 
or  tints,  the  latter  acquire  a  great  tendency — 
almost  as  great  as  that  of  the  high  lights — to 
be  acted  on  by  the  developer,  the  result  being, 
therefore,  when  the  subject  is  lighted  by  great 
oppositions  of  lights  and  shades  a  perfect,  or, 
at  least,  as  possible  a  perfect  picture  as  one 
can  obtain,  and  if  the  subject  is  normally 
lighted,  a  picture  wanting  in  contrasts  and 
solarized  in  the  high  lights,  that  is,  devoid  of 
half  tints,  the  whole  having  been  equallized,  so 
to  speak,  during  the  reversal  of  the  primary 
action  on  the  parts  in  question. 

On  the  other  hand,  if  the  exposure  time  is 
short,  the  half  lights,  being  in  proportions  to 
the  high  lights   little  impressed*  or  not  at 


*  The  effects  of  solarization  are  much  attenuated  by 
dying  the  photo  film,  (orthochromatic  plates). 


INTRODUCTION, 


all,  fail  to  develop  or  do  not  take  a  pro- 
portionate and  sufficient  opacity,  and  the 
result  is  a  picture  with  exaggerated  contrasts 
unless  the  subject  be  uniformly  lighted  when 
the  picture  will  be  improved  by  the  greater 
oppositions  between  the  lights  and  shadows 
resulting  thereof. 

As  it  is  seen  the  character  of  the  picture  can 
be  altered  by  varying  the  time  of  exposure. 
In  practice  this  is  sometimes  of  difficult 
application,  and  had  we  not  at  our  disposal  the 
means  to  annul,  or,  more  correctly,  to  attenuate 
the  defects  arising  from  over  or  short  ex- 
posure-times, it  would  be  a  matter  of  chance 
to  obtain  perfect  pictures.  These  means  we 
find  them  in  the  manner  of  conducting  the 
development  and  of  compounding  the  de- 
veloping solutions  either  to  force  the  half 
lights  to  develop  before  the  high  lights 
gain  intensity  or  to  cause  the  latter  to  intensify 
to  a  certain  extent  before  the  former  make 
their  appearance.  In  a  word  the  operator  by 
a  proper  management  of  the  chemicals  can 


INTRODUCTION. 


obtain  at  will,  so  to  say,  eitlier  softness  and 
harmony,  or  vigor  and  brilliancy. 

Hence  the  perfection  of  the  picture  depends 
not  only  of  the  exposure-time  but  also,  and 
principally,  of  the  development.  This  is  the 
most  important  operation  of  photography. 
It  requires  judgment  and  artistic  taste  io 
produce  photographs  of  faultless  beauty,  and 
much  experience  to  overcome  the  difficulties 
which  present  themselves.  We  hope  that  the 
beginner  guided  in  his  first  essays  by  the 
general  rules  given  in  this  book  with  examples 
of  their  applications  will  soon  master  them. 


PART  I. 


Chemistry  of  the  Keageots. 
Illumination  of  the  Dark  Room. 
The  Exposure  Time. 


CHAPTER  I. 


Chemistry  and  Behavior  of  the  Com- 
pounds Employed  to  Develop  the 
Photographic  Image. 


SALTS  OF  IKON. 

The  following  iron  salts  are  employed  in  the 
development  of  the  latent  image  :  Ferrous 
sulphate,  ferrous  oxalate,  and  ferrous  citrate. 

Ferkous  Sulphate,  Fe  S  O4.  Syn:  jproto- 
sulj)hate  of  iron,  green  vitriol,  copperas.  Ferrous 
sulphate  crystallizes  with  7  molecules  of  water ; 
it  therefore  contains  per  cent  5468  parts  of 
the  anhydrous  salt. 

The  crystals  are  greenish-blue  when  the  salt 
crystallizes  in  an  acid  s:lution,  and  emerald 
green  if  the  solution  contains  ferric  sulphate. 

It  is  not  venemous.  Its  test  is  styptic;  its 
reaction  strongly  acid.  All  the  oxidizing 
agents  transform  it  into  ferric  sulphate. 


4 


THE  PHOTOGRAPHIC  IMAGE. 


It  is  insoluble  in  absolute  alcohol.  Alcohol 
at  50^  dissolves  about  3  per  cent,  of  it. 

100  parts  of  f  10°  C.  dissolve   61  )  parts  of 

\  15°  C,      "        70  \ 
water  at     (  33°  C.      "       151  )  ferrous  sulphate. 

100  Darts  of      f  164  parts  of  water  at  10°  C. 

143     *'  "         15°  C 

ferrous  sulphate  1  <<  «<        24°  0* 

dissolve  in       [    66     *'  "        43°  c! 

Exposed  to  the  air  the  crystals  effloresce 
and  become  covered  with  an  ochreous  coating 
of  basic  ferric  sulphate,  (Fe203)2S04.  This 
oxidation  is  prevented  by  the  presence  of 
sugar,  glucose,  etc.;  the  oxygen  acts  then  on 
the  organic  substance  by  means  of  the  sul- 
phate which  serves  of  a  vehicle. 

The  solution  of  ferrous  sulphate  oxidizes  in 
the  air  by  absorption  of  oxygen  with  formation 
of  basic  ferric  sulphate  and  normal  ferric  sul- 
phate. Saccharine  substances  and  sulphuric 
acid  prevent  these  actions. 

Ferrous  sulphate  precipitates  the  soluble 
salts  of  silver  and  gold  to  metal. 

2  reS04  +  6  AgNOs  +  3  H,0=:(Fe203)  2  SO4+ 
6  HN03+Ag6.  (Davanne.) 

Ferric  Sulphate,  Fe2(S04)3.  Syn. :  iron  ses- 
quisulphatej  MonseVs  salt.     Ferric  sulphate  is 


CHEMI8 TRY  AND  BEHA  VIOR,  cfcc.  5 


yery  soluble  in  water.  It  dissolves  metallic 
silver  forming  argentic  and  ferrous  sulphate. 
This  property  is  utilized  in  photography  to 
reduce  the  intensity  of  negatives.  The  solu- 
tion saturated  by  the  aid  of  heat  deposits,  in 
cooling,  very  fine  crystals  of  metallic  silver, 
ferric  sulphate  being  regenerated,  thus  : 

Ag2S04+2  reSO,=Ag2+Fe2(S04)3. 

Ferrous  Oxalate,  FeC204,  is  obtained  by 
dissolving  iron  in  oxalic  acid,  or  by  exchange 
of  sases  by  treating  ferrous  sulphate  with 
neutral  potassic  oxalate  : 

It  crystalizes  in  small,  brilliant,  yellow  crys- 
tals. It  reduces  the  salts  of  silver,  but  being 
scarcely  soluble  in  water  it  is  employed  united 
to  the  potassic  oxalate  with  which  it  forms  a 
soluble  double  salts,  KaFe (0204)2.  100  parts 
of  a  saturated  solution  of  potassium  oxalate^ 
dissolve  12  parts  of  the  salt  in  question. 

The  use  of  ferrous  oxalate  as  a  developer 
was  suggested  by  Mr.  Oarey  Lea  in  1877.  The 


*  Potassium  oxalate  dissolves  in  3  parts  of  cold  water, 


THE  PHOTOGRAPHIC  IMAGE. 


developing  solution  is  prepared  bj  adding  1 
part  of  a  solution  of  ferrous  sulphate  at  30  per 
cent  of  water  to  3  parts  of  a  solution  of  neutral 
potassium  oxalate  at  the  same  strength. 

The  reduction  of  silver  haloids  by  ferrous 
oxalate  is  effected  by  the  dissociation  of  the 
elements  of  water.  The  chemical  actions 
occurring  during  the  reduction  are  as  follows : 

1st,  The  ferrous  oxalate  is  oxidized  with 
formation  of  ferric  oxalate  and  ferric  oxide 
in  displacing  the  oxygen,  hydrogen  being 
set  free  : 

2nd,  Then  the  hydrogen  in  the  nascent  state 
reduces  the  silver  salt  by  combining  with 
bromine : 

AgBr+H=HBr+Ag : 

3rd,  And  hydrobromic  acid  uniting  with  the 
ferric  oxide  forms  ferric  bromide  and  water : 

6HBr+Fe203=re2Bre+3  H2O. 

The  ultimate  result  is  represented  by  the 
following  equation  : 

6  FeCA+6  AgBr=:2  Fe^CCaOOs+Fe^Bre+Age. 


CHEMISTRY  AND  BEHAVIOR,  &c. 


7 


With  potassium  ferrous  oxalate,  potassium 
bromide  is  formed : 

re2Br6+3  'K,G20,=6  KBr+Fe2(C204)3. 

The  chemical  actions  taking  place  during  the 
development  with  pyrogallol,  hydroquinone 
and  other  developers  are  similar :  the  reduc- 
tion of  the  silver  haloid  is  effected  through 
the  agency  of  hydrogen  dissociated  from 
water  uniting  to  the  haloid. 

Fereous  Citrate,  re3(C6H507)2 ,  is  prepared 
by  double  decomposition  for  photographic  use. 
It  was  selected  by  Eder  and  Pizzighelli  for 
the  development  of  emulsion  with  silver 
chloride^  as  acting  less  energetically  than 
ferrous  oxalate.  It  is  now  little  used.  Three 
stock-solutions  should  be  at  hand  to  com- 
pound the  developer,  viz.; 

A.  Ammonium  citrate  solution.  Dissolve  by 
the  aid  of  heat  600  grains  of  citric  acid  in 
4J  ounces  of  water,  and  neutralize  by  aqueous 
ammonia ;  drive  out  the  excess  of  ammonia  by 
heating,  then  dissolve  400  grains  of  citric  acid 
and  add  water  to  make  up  9  ounces. 

*  This  emulsion  is  used  for  transparencies.  Negativea 
can  also  be  made  with  the  same. 


8 


THE  PHOTOGRAPHIC  IMAGE. 


B.  Ferrous  sulphate  solution.  1  to  3  of  water 
with  a  few  drops  of  sulphuric  acid  to  prevent 
oxidation. 

C.  Sodium  cJdoride  Solution.  1  to  30  of  water. 
To  develop,  these  solutions  are  mixed  in  the 

following  proportion : 

A  ...  30 
B  ...  15 
C     .     .     .  3 

Sodium  chloride  is  an  energetic  restrainer. 
It  should  be  employed  judiciously.  The 
ferrous  sulphate  solution  employed  in  greater 
proportion  than  that  above  given  retards  the 
development. 

By  diluting  the  developer  less  intensity  is 
obtained,  which  in  case  of  under  exposures, 
etc.,  is  advantageous. 

Gallic  acid  added  to  the  developer  produces 
a  sepia  tone  and  acts  as  an  accelerator.  To 
the  above  solution  5  parts  of  a  saturated 
solution,  can  be  added. 

Potassium  Feekocyanate,  (FeCye).  It 
crystallizes  with  3  molecules  of  water  in 
yellow  prisms  or  tables  insoluble  in  alcohol, 
soluble  in  4  parts  of  cold  water.    Its  taste  is 


CHEMISTRY  AND  BEHAVIOR,  &c.  9 


sweetish  at  first,  then  salted  and  bitter.  It  is 
not  poisonous. 

Chlorine,  bromine,  dilute  nitric  acid,  all  the 
oxidizing  agents  capable  of  displacing  potas- 
sium transform  it  into  ferricjanate  : 

2  K4(FeCy6)+Br2=:K6(Fe2Cyi2)+2  KBr. 

The  silver  salts — chloride,  bromide,  nitrate 
— decompose  it  with  formation  of  the  double 
cyanide  of  potassium  and  silver  under  the 
influence  of  heat. 

K4(reCy6)+2  AgCl=FeCy2+2  KAgCy2+2KCL 

Potassium  ferrocyanate  was  recommended 
by  Mr.  A.  L,  Henderson  in  conjunction  with 
the  pyrogallol  developer.  It  is  also  employed 
with  hydroquinone  and  eikonogen.  Per  se  it 
possesses  no  reductive  property.  Some 
authors  assert  that  it  causes  a  softer  image  to 
be  developed,  others,  amongst  which  Mr.  E. 
Himly  who  studied  his  action  with  hydro- 
quinone, that  the  addition  of  a  few  drops  of  a 
solution  of  the  salt  at  30  per  cent  of  water  is 
advisable  to  obtain  more  contrasts.  The 
author  of  thip  book  has  ascertained  that  it 
effectively  prevented  fogging  and  consequently 
acted  as  a  weak  restrainer,  but  thinks  that  in 


Id  'I HE  PRO TOGRAPHIC  IMA G^. 


the  whole  it  can  be  discarded,  moreover,  any 
change  advisable  in  the  character  of  the 
negatives  is  easily  effected  by  compounding 
the  developing  solution  with  more  or  less 
reagent  or  more  or  less  alkali  and  the  usual 
restrainer  KBr.* 

Potassium  Feericyanate,  K6(re2Cyi2),  crys- 
tallizes without  water  of  crystallization  in 
rhomboidal  crystals  of  a  ruby-red  color, 
unalterable  in  the  air  and  soluble  in  2 J  parts 
of  cold  water,  the  solution  under  the  influence 
of  light  depositing  a  blue  powder  with  forma- 
tion of  ferrocyanate.  In  presence  of  organic 
matters  it  is  likewise  reduced. 

It  attacks  zinc,  copper,  lead,  mercury,  silver 
which  it  transforms  into  ferrocyanate,  being 
itself  reduced  to  a  similar  compound.  This 


*  We  have  used  as  an  energetic  developer : 

A.  Sodium  sulpiiite,    .       .  40  parts. 
Potassium  ferrocyanate,  .20 
Hydroquinone,      .       .  10  •* 
Water,      .      .       .  480  *' 

B.  Sodium  hydrate,    .       .     30  parts. 
Water,       .       .       .      480  " 

Equal  volumes  for  rapid  exposures. 


Chemistry  AND  behavior,  dc. 


11 


action  is  utilized  for  the  reduction  of  over 
dense  cliclies  (Farmer's  process). 

PYROGALLOL. 

Pyrogallol,  aHA=C6H3(OH)3.  Syn  :  Tri- 
oxyhenzine,  pyrogallic  phenol,  j^y^'ogallic  acid. 
Pyrogallol  is  venemous,  causing  death  at  the 
dose  of  from  2  to  3  grams  in  acting  as  phos- 
phorous by  absorption  of  oxygen  from  the 
blood. 

It  occurs  in  prisms  or  in  long  needles  which 
are  perfectly  white. 

It  blackens  in  damp  air,  the  action  being 
more  rapid  in  the  light.  The  products  of  the 
decomposition  are  brown-black  matters  whose 
constitution  has  not  been  ascertained,  plus 
oxalic  and  acetic  acid  and  carbon  dioxide  : 

C6He03+0,=C2HA+C2HA+2  CO,. 
Its  taste  is  faintly  bitter,  its  odor  nul,*  its 
reaction  neutral.t    It  melts  at  115°  C,  boils  at 

*  The  commercial  pyrogallol  has  generally  an  empy- 
reumatic  odor.  If  it  deposits  a  black  substance  it 
contains  metagallic  acid  which  is  insoluble. 

t  Litmus  paper  turns  slightly  red,  but  assumes  its 
original  blue  color  in  drying,  exactly  as  when  reddened 
by  carbonic  acid. 


12 


THE  PHOTOGRAPHIC  IMAGE. 


210^  C,  and  at  250^  C,  splits  into  metagallic 
acid  and  water,  thus  : 

C6He03=C6H,0,+H20. 

Pjrogallol  is  soluble  in  2|  parts  of  water  at 
15^  C,  1|  part  of  alcohol  at  90^  and  in  1|  part 
of  ether.  The  aqueous  solution  turns  black  in 
the  air  by  absorption  of  oxygen,  depositing 
black  flocks  and  evolving  carbon  dioxide. 
Sulphurous  acid,  the  alkaline  sulphites,  citric, 
oxalic,  and  formic  acids,  traces  of  nitric  acid 
prevent  this  decomposition.  The  alcoholic 
solution  is  more  staple  and  keeps  for  a  long 
time,  it  being  little  altered. 

In  presence  of  the  alkalies,  of  the  alkaline 
carbonates  and  aqueous  ammonia,  pyrogallol 
rapidly  absorbs  oxygen,  becomes  yellowish, 
then  brown  and  lastly  brown-black  with  forma- 
tion of  carbon  dioxide  (carbonic  acid),  acetic 
acid,  oxalic  acid,  etc.,  and  traces  of  hydrogen 
dioxide. 

It  does  not  decompose  the  carbonates. 
Boiled  with  potassium  hydrate  pyrogallol  is 
decomposed  into  carbon  dioxide,  acetic  and 
oxalic  acids.  Added  to  lime  water,  the  liquid 
assumes  a  fine  red  tint  which  turns  brown. 


CHEMISTRY  AND  BEHAVIOR,  &g 


13 


This  action  is  \ery  delicate.  It  serves  in 
analyses. 

Hydrochloric  acid  has  no  action  on  pyro- 
gallol. 

Nitric  acid  transforms  it  into  oxalic  acid. 

Nitrous  acid  and  the  nitrites  even  in  very 
small  quantities  turn  brown  its  solution. 
This  action  serves  to  detect  infinitesimal 
traces  of  these  compounds. 

Chlorine  decomposes  pyrogallol  in  precipi- 
tating a  black  substance  and  forming  hydro- 
chloric acid. 

Bromine  forms  an  insoluble  bromized 
derivative  BrsfCeHsOs)  which  first  becomes 
deep  red  in  presence  of  the  alkalies  and  then 
turns  red-brown  in  the  air. 

Ammonia  precipitates  from  the  ethereal 
solution  of  pyrogallol,  white  crystals  of  a 
compound  termed  ammonium  pyrogallate 
CfiHsNH^,  which  rapidly  oxidizes  in  the  air 
with  formation  of  pyrogallein. 

Potassium  permanganate  decomposes  it, 
liberating  carbon  dioxide  with  effervescence  in 
concentrated  solution.  The  permanganate  is 
decolored. 

Heated  with  anhydrous  phthalic  acid,  it  is 


THE  PHOTOGRAPHIC  IMAGE. 


converted  into  gallein,  which  treated  by  hot 
sulphuric  acid  yields  a  very  staple  green 
coloring  matter,  the  coerulein  employed  in 
orthochromatic  photography. 

Pyrogallol  unites  with  gelatine  and  casein. 
It  gives  with  ferric  chloride  a  red  coloration 
turning  black  progressively.  It  colors  the 
skin  and  hairs  brown-black.* 

It  reduces  the  salts  of  silver,  gold  and 
platinum.  In  silver  nitrate  solutions  it  dis- 
sociates the  metal,  depositing  a  red  compound 
termed  purpurogallein,  C20H10O9,  which  oxidizes 
rapidly. 

Pyrogallol  is  obtained  from  gallic  acid  which 
under  the  influence  of  heat  splits  into  carbon 
dioxide  and  the  compound  in  question  : 
C6H3.CO,(OH)3=CeH3(OH)3+CO,. 

In  manufactures  it  is  obtained  from  nut- 
galls  which  yields  about  12  per  cent  of  it. 
The  dry  extract  is  placed  in  an  iron  vessel 
heated  to  180^  C.  on  a  sand  bath  and  covered 
with  a  receiver  into  which  pyrogallol  subli- 
mates and  condenses  in  prisms. 

*  Stains  on  the  hands  can  be  removed  by  a  dilute 
solution  of  sulphuric  acid  1.100,  or  of  hydrochloric  acid 
5.100  or  bv  citric  acid  or  any  clearing  solution. 


CHEMISTRY  AND  BEHAVIOR,  &c.  15 


HYDEOQUINONE. 

Hydkoquinone,  C6H602=  C6H4(0H)2.  Syn : 
Quinolj  Paradioxyhenzene.  Hydroquinone  is  a 
diatomic  phenol  isomeric  witli  catechol  and 
resorcinol.  It  is  formed  by  the  action  of 
di oxidizing  agents  such  as  sulphur  dioxide, 
hydriodic  acid,  stannic  acid,  etc.,  on  quinone 
which  takes  up  a  molecule  of  hydrogen, 
C6Hi02+H2=C6H602,  or  by  oxidizing  aniline 
with  potassium  bichromate.  It  is  by  the 
latter  process  that  it  is  produced  in  manufac- 
tures, thus  :  one  part  of  aniline  and  8  parts  of 
sulphuric  acid  are  dissolved  in  30  parts  of 
water  and  the  mixture  allowed  to  cool.  Two 
and  a  half  parts  of  pulverized  potassium 
bichromate  are  then  little  by  little  added, 
taking  care  to  keep  cold  the  solution,  whereby 
among  other  products  hydroquinone  is  formed 
together  with  quinone.  A  current  of  sulphur 
dioxide  now  passed  through  the  solution 
transforms  the  quinone  into  hydroquinone 
which  is  taken  up  by  ether.  The  ethereal 
solution  rises  on  the  surface  and,  the  aqueous 
liquid  being  drawn  off,  the  ether  by  evapora- 
tion leaves  a  residue  which  is  dissolved  in  a 


16 


THE  PHOTOGRAPHIC  IMAGE. 


small  quantity  of  hot  water,  and  from  this 
solution  treated  by  sulphur  dioxide,  decolor- 
ized with  animal  charcoal,  boiled,  filtered,  and 
cooled,  hydroquinone  is  deposited. 

Hydroquinone  crystallizes  in  orthorhombic 
prisms  without  taste  and  odor,  and  without 
action  on  test  paper.  When  the  crystallization 
is  slow  the  crystals  are  lemon-yellow  and 
contain  27.2  of  water  per  100.  But  if  formed 
rapidly,  they  are  very  white  and  take  up  only 
12.8  parts  of  water. 

It  is  soluble  in  ether  and  alcohol.  Water, 
at  15°  C.  dissolves  6  per  100  of  it,  and  9.5  parts 
at  the  temperature  of  30°  C.  It  melts  at 
169°  C,  and  when  gradually  heated  it  subli- 
mates easily  as  brilliant  scales  without 
alteration.  It  is  on  this  form  that  it  is 
generally  found  in  commerce. 

It  reduces  in  the  cold  the  salts  of  mercury, 
silver,  gold  and  platinum  with  formation  of 
quinone  by  elimination  of  hydrogen  : 

C6Ht502  =  H^-j-  C6H4O2. 

According  to  H.  Eeele,  8  parts  of  hydro- 
quinone reduce  68.22  of  silver  oxide. 

The  reductive  property  of  hydroquinone  is 


CHEMISTRY  AND  BEHAVIOR,  &c. 


17 


increased  by  the  hydrates  and  carbonates  of 
the  alkali  metals,  it  being  transformed  by 
oxidation  into  quinone,  green  hydroquinone 
and  brown  substances  analogous  to  those 
formed  by  the  oxidation  of  pyrogallol.  The 
solution  is  first  tinged  yellow,  then  turns  red- 
brown  and  possesses  tinctorial  properties. 
Fer  se  hydroquinone  does  not  reduce  the  silver 
haloids. 

Hydroquinone  is  not  precipitated  by  lead 
acetate.  It  dissolves  without  alteration  in 
normal  and  acid  sulphites  solutions  from 
which  it  deposits  as  yellow  crystals  containing 
sulphurous  acid.  These  solutions  are  almost 
inalterable  in  the  air  and  keep  well  even  in 
presence  of  an  alkali. 

Nitric  acid  transforms  hydroquinone  into 
oxalic  acid. 

Chlorine,  ferric  chloride,  potassium  bichro- 
mate, silver  nitrate  and  other  oxidizing  agents 
convert  it  into  quinone  and  an  hydroquinone 
crystallizing  in  needles  with  a  beautiful  green 
lustre.  This  compound.  Green  hydroquinone, 
C6O5O2,  is  soluble  in  ether  and  alcohol.  Sul- 
phur dioxide  resolves  it  into  colorless  hydro- 
quinone.   Treated  by  ammonium  hydrate  and 


18  THE  PHOTOGRAPHIC  IMA GE. 


the  alkalies  it  rapidly  absorbs  oxygen,  being 
converted  into  a  red-brown  coloring  matter. 

Hydroquinone  forms  derivatives  with  the 
haloids.  Its  use  in  photography  was  suggested 
by  Captain  W.  de  W.  Abney,  in  1880. 

EIKONOGEN. 

/-'SO.Na 
C,oH5<  OH 

This  compound  is  the  sodium  salt  of  Amido 
^-Naphtol  ^-monosulphonic  acid,  discovered 
in  1881,  by  professor  Eaphael  Meldola. 

It  crystallizes  with  2  molecules  of  water  in 
semi  opaque  yellowish-white  crystals  having  a 
shining  lustre.  Its  taste  is  sweetish  and  pecul- 
iar, its  smell  prickly.  It  slowly  evolves  acid 
fumes  in  being  decomposed. 

It  is  insoluble  in  alcohol,  dissolves  with 
difficulty  in  cold  water  which,  however,  retains 
at  common  temperatures  from  7  to  8  parts 
per  cent  when  the  solution  has  been  effected 
by  heat.  According  to  a  well  known  law  of 
chemistry,  it  is  precipitated  from  its  solution 
\>j  the  addition  of  a  more  soluble  salts,  sodium 


CHEMISTRY  AND  BEHAVIOR,  &c.  l9 


sulphite,  carbonate,  etc.  We  found  that  in  an 
aqueous  solution  containing  per  cent  5  parts 
of  normal  sodium  sulphite  only  4  parts  of 
eikonogen  can  be  dissolved.  As  pyrogallol 
and  hydroquinone,  eikonogen  possesses  tinc- 
torial properties  when  oxidized,  the  dyed 
substance,  gelatine,  being  greenish  by  reflec- 
tion and  pink  by  transparency. 

Eikonogen  reduces  silver  nitrate  in  acid 
solutions,  but  per  se  it  has  nq  action  on  the 
haloid  salts  of  that  metal  without  the  inter- 
vention of  an  alkali.  HowevQr,  the  reduction 
takes  place,  although  slowly,  yielding  very 
clear  negatives,  in  presence  of  sodium  sulphite, 
which  may  be  explained  by  the  alkaline  reac- 
tion of  the  salt. 

With  an  alkali  to  form  a  more  reductive 
compound,  eikonogen  reduces  almost  instanta- 
neously the  silver  haloids  impressed  by  light ; 
but  notwithstanding  such  a  powerful  reducing 
action,  by  equal  weight,  it  absorbs  four  times 
less  oxygen  than  hydroquinone  (H.  Reeb)  and 
still  less  than  pyrogallol.  The  energy  of  its 
action  is  therefore  soon  impaired,  and  this 
explains  why  during  the  development  the 
image,  which  rapidly  appears  in  all  its  details 


20  THE  PHOTOGRAPHIC  IMAGE. 


slowly  intensifies,  and  why  it  should  be  em- 
ployed in  larger  quantity  than  the  other  re- 
agents to  obtain  strong  negatives. 

According  to  Mr.  H.  Eeeb,  8  parts  of  hydro- 
quinone  make  the  work  of  33  parts  of  eikon- 
ogen,  these  quantities  reducing  100  parts  of 
silver  nitrate,  or  the  equivalent  of  silver  oxide, 
with  the  same  dose  of  alkali :  40  parts  of 
potassium  carbonate  or  23.53  parts  of  sodium 
hydroxide. 


HYDEOXYLAMINE  OE  OXYAMMONIA. 


This  base  discovered  by  Lossen,  in  1865,  is 
considered  as  ammonia  in  the  constitution  of 
which  a  molecule  of  hydroxyl  is  substituted  to 
one  atom  of  hydrogen,  thus  : 


It  is  formed  by  the  action  of  hydrogen  on 
nitrogen  oxide.  This  mode  of  formation  is 
similar  to  that  of  ammonia  when  the  oxide  and 


CHEMIS  TR  Y  AND  BEHA  VI OR,  &c.  21 


hydrogen  in  excess  are  simultaneously  passed 
on  heated  platinum  sponges,  thus  : 

NO+H3=NH20H  and  NO+H5=NH40H 

All  the  salts  of  hydroxylamine,  like  those  of 
ammonium,  are  decomposed  by  the  alkalies 
which  set  free  hydroxylamine. 

Hydroxylamine  possesses  powerful  reducing 
properties.  It  reduces  the  salts  of  aluminum, 
zinc,  iron,  lead,  silver  and  gold,  and  transforms 
manganese  dioxide  into  monoxide. 

It  converts  mercuric  chloride  into  calomel 
and,  in  excess,  precipitates  it  to  metallic  state. 

Hydroxylamine  has  not  been  isolated.  It  is 
known  only  in  solution  or  combined  to  acid 
radicals.  A  pure  solution  is  best  obtained 
from  the  sulphate  treated  by  calcium  hydrate : 

(NH30)2S04  +  Ba(OH)2  =  BaS04+2  NH3O+ 
OH2. 

It  is  decomposed  by  the  alkalies  into  nitro- 
gen and  ammonia,  the  action  progressing  so 
much  more  rapidly  as  the  solution  is  more 
cencentrated  : 

3  NHsO^N^+NHs-l-.S  HA 

The  chloride  and  nitrate  of  hydroxylamine 


22 


THE  PHOTOGRAPHIC  IMAGE. 


are  soluble  in  water  and  in  alcohol.  The  sul- 
phate is  precipitated  by  alcohol  from  its  aque- 
ous solution. 

Hydroxylamine  procipitates  cuprous  oxide 
from  cupric  sulphate  in  hot  solutions. 

As  a  developer  in  the  gelatine  process, 
hydroxylamine  was  suggested  by  Spiller  and 
Egli,  either  alone  or  in  conjunction  with  pyro- 
gallol.  It  yields  very  clear  negatives.  The 
ultimate  action  is  represented  by  the  following 
equation : 

2  NH3O  +  4  AgBr  +  4  KOH=  4  KBr  +N2O+ 
5  OH,+Ag,. 

In  the  arts  it  is  employed  in  calico  printing 
to  form  reserves. 

For  our  purpose  it  is  obtained  from  the 
chlorhydrate  treated  by  an  alkali,  and  acts 
while  in  the  nascent  state  with  great  energy. 

The  chief  advantage  of  hydroxylamine  as  a 
developer  is  not  to  absorb  oxygen  from  the  air. 
Its  solution  is  therefore  inalterable.  It  is  little 
employed  on  account  of  the  evolution  of 
nitrous  oxide,  N2O,  which  gives  rise  to  blisters 
in  the  gelatine  process. 


OHEMIBTEY  AND  BEHAVIOR,  &c.  23 


THE  HYDKOXIDES   (HYDKATES)  AND 
CAKBONATES  OF  THE  ALKALI- 
METALS. 

Potassium,  sodium,  ammonium,  and  lithium 
hydroxides  are  employed  in  the  development 
of  the  latent  image.  Their  action  consists  to 
increase  the  reductive  power  of  the  reagent  by 
exalting  its  affinity  for  oxygen,  but  see  further 
on. 

Whatever  be  the  hydroxide  employed  the 
ultimate  result  is  the  same . 

When  substituting  an  hydroxide  for  another 
in  formulas  one  should  take  into  account  their 
equivalence  which  necessarily  varies  with  that 
of  the  metal. 

The  following  table  shows  the  equivalences 
of  the  hydroxides  : 


Potassium.       Sodium.  Lithium. 

KOH  —  NaOH  —  LiOH 

56      =      40  =  24 

1.     =       0.714  =  0,428 

1.4  =       1.  =  0.6 

1.5  =       1.666  =  1. 


24  THE  PHO  TOGRAPHIC  IMA  GE. 


Ammonium  hydrate  being  very  volatile  and 
sold  in  solutions  at  various  strengths,  it  is  not 
possible  to  give  any  data  for  the  equivalence. 

The  carbonate  of  these  bases  are  also  em- 
ployed for  the  purpose  in  question.  They  act 
as  the  hydrates  but  with  less  energy,  and  not 
possessing  so  strong  caustic  properties,  they  do 
not  disorganize  organic  substance  so  rapidly. 
For  this  reason  when  the  gelatine  film  blisters 
with  a  developer  prepared  with  the  alkalies, 
the  carbonates  should  be  substituted. 

The  following  table  shows  the  equivalences 
of  potassium  and  sodium  carbonates : 


K2CO2  NaaCOs 
Anhydrous.+2  H2O.     Anhydrous. +10  H2O.  +5  HjO. 


138 

=  174 

=  106 

286 

196 

1. 

=  1.261 

=  0.768 

2  072 

1.421 

0.793 

=  1. 

=  0.919 

1.643 

1.126 

1.301 

=  1.641 

=  1. 

2.698 

1.849 

0.443 

=  0.608 

=  0.370 

1. 

0.685 

0.709 

=  0.887 

=  0.592 

1.459 

1. 

The  ammonium  carbonates  are  volatile. 
No  data  can  be  given.  They  are  employed 
by  few  operators. 


CHEMISTRY  AND  BEHAVIOR,  &c.  25 


Potassium  Hydroxide  or  Hydrate,  K0H= 
56,  is  commonly  known  nnder  the  name  of 
caustic  potash  to  distinguish  it  from  the  potash 
of  commerce  which  is  an  impure  carbonate. 

Potassium  hydroxide  is  a  hard,  white  sub- 
stance possessing  energetic  basic  property, 
very  caustic,  soluble  in  alcohol,  exceedingly 
deliquescent  and  consequently  very  soluble  in 
water. 

It  softens  the  skin  and  progressively  dis- 
solves it,  disorganizes  numerous  organic  mat- 
ters, neutralizes  all  the  acids  and  dissolves 
fatty  and  resinous  substances  by  uniting  with 
their  acid  radicals. 

It  decomposes  glasses,  especially  those  con- 
taining lead,  and  porcelain,  poteries,  etc.,  by 
dissociating  the  aluminia  and  the  silicates. 
Potassium  carbonate  acts  in  the  same  manner. 

In  chemistry  it  is  employed  to  precipitate 
the  insoluble  oxides  from  their  combinations. 
It  is  the  best  reagent  to  detect  the  ammonium 
salts,  liberating  ammonia  which  is  readily 
recognized  by  its  characteristic  smell. 

Potassium  Carbonate,  K2C03=138.  This 
salt  is  white  and  deliquescent.    In  contact 


26 


THE  PHOTOGRAPHIC  IMAGE. 


witli  the  air  it  absorbs  carbon  dioxide,  being 
transformed  into  bicarbonate.  It  dissolves  in 
its  weight  of  water.  To  obtain  a  solution  at 
.100  per  100,  it  should  be  dissolved  in  100 
c.  cm.  of  water  in  a  quantity  sufficient  to  form 
a  volume  of  143  c.  cm. 

It  crystallizes  with  two  molecules  of  water. 
Its  reaction  is  strongly  alkaline.  It  contains 
per  cent  54.02  parts  of  potassium  oxide,  K2O. 

There  are  three  grades  of  potassium  carbon- 
ate sold  in  commerce,  viz.  :  potash  which  is 
quite  impure,  containing  about  60  per  100  of 
carbonate  mixed  with  chloride,  sulphate  and 
silicate  of  potassium  in  various  proportions  ; 
pearlasJif  which  is  purer ;  and  salt  of  tartar 
containing  but  a  small  quantity  of  chloride. 
The  latter  can  be  employed  instead  of  the 
chemically  pure  compound. 

Sodium  Hydeoxide  or  Hydrate,  NaOH  = 
40.  The  properties  of  this  base  are  similar 
to  those  of  potassium  hydrate,  although  some- 
what less  energetic.  As  the  latter  it  is  deli- 
quescent in  the  air  from  which  it  absorbs  car- 
bon dioxide  in  being  transformed  into  carbon- 
ate.   It  crystallizes  with  7  molecules  of  water. 


CHEMIST R  Y  AND  BEHA  VIOR,  &c. 


27 


It  is  sold  under  tlie  name  of  caustic  soda. 
The  soda  of  commerce  is  an  impure  carbonate. 

The  salts  of  sodium  color  the  flame  of 
alcohol  yellow. 

Sodium  Carbonate,  NaaCOs-  Sodium  car- 
bonate is  white,  its  taste  caustic  and  acrid, 
its  reaction  strongly  alkaline.  It  crystallized 
with  10  molecules  of  water  of  which  it  loses 
5  in  efflorescing  in  the  air.  Crystals  with  seven 
molecules  of  water  are  obtained  from  the 
mother  waters  of  crystallization  of  the  com- 
pound with  10  H20.^- 

The  crystals  with  10  H2  O  contains  62.94  of  water  per  100 
7H2O  54.31 
«*        ««     5H2O      «'      45.92  " 

100  parts  of  water  at  f  1^°  C.  dissolves  16.65  parts  of  salt. 

\  20°  C.       "  25.83 
the  temperature  of    l30°C.       "       30.83     **  " 

It  is  insoluble  in  alcohol. 

The  sodium  carbonate  of  commerce — wash- 
ing soda — is  very  impure,  containing  about  3 
per  100  of  various  salts  :  sulphite,  thiosulphate 


*  For  this  reason  the  commercial  article  contains 
variable  quantities  of  water  of  crystallization. 


28 


THE  PHOTOGRAPHIC  IMAGE. 


(hyposulphite),  silicate,  chloride,  and  sometimes 
traces  of  cyaiaide,  ferrocyanide,  sulphocyanate, 
besides  iron  and  lead  oxides. 

Ammonium  Hydeate^  NHiOH^SS.  This  is 
one  of  the  most  energetic  bases.  Its  fumes  are 
suffocating.  They  are  neutralized  by  acetic 
acid. 

The  aqueous  solution  concentrated  at  26° 
Baume  contains  35  per  100  of  gaseous  am- 
monia. The  solution  is  not  permanent.  The 
water  gives  off  all  the  gas  when  heated  to  60° 
C,  or,  gradually,  in  open  vessel  at  ordinary 
temperatures.  In  contact  with  the  air  it 
absorbs  carbon  dioxide,  being  converted  into 
carbonate. 

The  concentrated  solution  of  ammonia  dis- 
solves without  alteration  chloride  and  bromide 
of  silver,  the  latter  sparingly. 

Ammonia  forms  with  iodine,  silver  oxide, 
gold  and  platinum  chlorides — dangerous  com- 
pounds which  explode  often  spontaneously 
or  under  a  slight  friction. 

Ammonia  is  employed  to  cauterize  the  bites 
of  venomous  reptiles,  bees,  etc.,  to  dissolve 
carmine,  to  clean  clothes  by  mixing  it  with  two 


CHEMISTRY  AND  BEHAVIOR,  dc. 


29 


parts  of  alcoliol.  As  a  base ;  it  is  employed 
to  instantly  neutralize  the  fumes  of  acids  and 
their  disorganizing  action  on  the  skin  and  on 
cloths  and  fabrics,  of  which  it  generally  revives 
the  color  if  applied  at  once. 

Ammonium  Hydrogen  Carbonate  (Bicarbon- 
ate), HNH4CO3.  This  salt  spontaneously 
evaporates  in  the  air,  emitting  the  character- 
istic odor  of  ammonia.  It  is  insoluble  in  alco- 
hol, soluble  in  8  parts  of  water  to  which  it 
imparts  a  strong  alkaline  reaction.  Heated  to 
36^  C,  it  is  decomposed  with  evolution  of  car- 
bon dioxide.     Boiling-water  decomposes  it. 

The  carbonate  of  ammonia  of  the  druggists, 
commonly  termed  sesquicarbonate,  is  a  mixture 
of  bicarbonate  and  carbamate  of  ammonium, 
HNH^COs+NH^CO^NH^. 

Ammonium  Sesquicarbonate,  H2(NH4)4(C03)3. 
The  reaction  of  the  sesquicarbonate  is  strongly 
alkaline,  its  taste  caustic  and  its  odor 
ammoniacal.  It  crystallizes  in  transparent 
octahedral  prisms  with  4  molecules  of  water. 
It  is  unstable,  rapidly  evolving  ammonia  in 
being  transformed  into  bicarbonate. 


30 


THE  PHOTOGRAPHIC  IMAGE. 


25  parts  dissolve  in  100  parts  of  water  at  13°  C. 
30     "         "  *'     *'  *«         17°  C. 

37    "  *'     **  *'         32°  C. 


"What  are  the  actions  of  the  alkalies  in  the 
development  ? 

The  principal  action  is,  as  we  have  said,  to 
increase  the  property  of  certain  developers  to 
absorb  oxygen  and,  thereby,  to  possess  a  more 
energetic  reducing  action.  That  needs  no 
comment ;  it  is  a  scientific  fact.  But  besides 
this  and  neutralizing  the  hydracids  formed  by 
the  reduction  of  the  silver  haloids,  there  is  a 
secondary  action  which  is  most  important, 
occurring  with  every  reagent,  and  permitting 
one  to  conduct  the  development  at  will,  so  to 
say. 

It  has  been  shown  by  Mr.  Henry  T.  Anthony 
(June,  1862)  that  when  a  dry  plate  is  exposed 
to  gaseous  ammonia  before  beiiig  subjected  to 
the  luminous  influence,  its  sensitiveness  is 
increased  considerably — this  was  the  starting 
point  of  the  alkaline  development — and  Dr. 
von  Monckhoven  has  demonstrated  that  am- 
monium hydrate,  a  caustic  alkali,  acts  on  silver 
bromide  as  does  heat  when  preparing  the 


CHEMISTRY  AND  BEHAVIOR,  i&c.  31 


emulsion,  that  is,  causes  certain  changes  in  the 
molecular  arrangement  of  the  constitutive 
elements  of  the  salt,  Ag  and  Br,  which  renders 
the  salt  exceedingly  sensitive  to  light.  There- 
fore it  is  admissible,  and  experiment  proves  it, 
that  the  alkalies  act  somewhat  in  a  similar 
manner  during  the  development  and  predispose 
the  silver  haloids  to  dissociation.*  The  whole 
silver  film  is  necessarily  acted  on,  and  if  the 
alkali  be  in  great  excess  a  general  reduction 
takes  place  before  the  details  and  density  are 
obtained.  This  is  termed  fogging.  But  when 
employed  at  certain  doses  to  act  independently 
from  the  reducing  agents  to  which  they  unite 
and  of  which  beyond  a  certain  limit  they  do  no 
more  as  a  consequence  increase  the  reductive 
property,t  the  alkalies  if  not  enough  pow- 
erful to  cause  a  general  reduction,  act, 
however,  on  the  parts  already  modified  by 
light.  Therefore  the  parts  impressed  by 
weak  lights — those  forming  the  half-tints  of 
the  picture — acquire  a  greater   tendency  to 

*  A  boiling  solution  of  potassa  or  soda  converts  silver 
chloride  into  oxide  which  is  rapidly  reduced  to  metal  by- 
sugar,  glucose,  etc. 

t  See  Pyrogallol. 


32  THE  PHO TOGRAPHIC  IMA GE. 


reduction,  and  if  the  reductive  power  of  tlie 
developer  is  not  energetic,  as  it  happens  when 
the  reagent  is  employed  in  small  proportions, 
these  parts  in  presence  of  free  alkalies  will 
develop  sometimes  simultaneously  with  the 
most  impressed,  and  in  every  case,  except 
when  the  exposure  is  insufficient,  before  the 
latter  acquire  a  great  intensity. 

The  reader  should  bear  in  mind  these  actions 
of  the  alkalies ;  their  judicious  applications 
during  the  development  are  of  the  greatest 
importance  to  obtain  good  negatives. 

The  carbonates  act  necessarily  with  less 
energy  than  the  caustic  alkalies  and  permit  to 
increase  the  dose  with  less  danger  of  produc- 
ing fogging  or  blistering. 

The  alkalies — caustic  ammonia  excepted — 
act  too  energetically  with  pyrogallol  which 
then,  by  rapidly  absorbing  the  atmospheric 
oxygen,  soon  exhausts  its  reductive  power. 

For  1  of  pyrogallol  1^  parts  of  K2CO3  is  a 
normal  dose ;  3  parts  is  a  large  dose ;  5  parts 
is  a  maximum.    Water,  100  parts. 

For  1  of  pyrogallol  2  parts  bf  NagCOs  is  a 


CHEMISTRY  AND  BEHAVIOR,  dtc.  33 


normal  dose  ;  4  parts  a  large  dose ;  6  parts  a 
maximum.    "Water  100  parts.* 

For  1  of  liydroquinone,  dissolved  in  100  parts 
of  water,  from  3  to  15  parts  of  NaaCOs  have 
been  employed.  Bouillaud  uses  for  instanta- 
neous exposures  as  much,  as  25  parts,  and  6  of 
sodium  sulphite. 

With  the  same  quantity  of  hydroquinone 
from  3  to  12  parts  of  K2CO3  or  from  1  to  4 
parts  of  caustic  soda  are  used.  Himly  com- 
pounds the  bath  with  2  parts  of  hydroquinone, 
14  parts  of  sodium  sulphite,  7  parts  of  NaOH 
and  100  parts  of  water. 

When  using  large  doses  of  alkalies  it  is 
advisable  to  add  a  restrainer,  say,  ^  part 
of  potassium  bromide  per  cent. 

THE  SULPHITES. 

NoEMAL  or  Neutral  Sodium  Sulphite, 
NasSOs,  crystallizes  with  10  molecules  of  water, 
but  more  often  with  7  molecules.  The  former 
consequently  contains  per  cent  58.82  parts  of 
water  and  the  latter  50  parts. 

*  At  the  same  dose  potassium  carbonate  acts  more 
energetically  than  the  sodium  salt  on  the  silver  haloids. 


THE  PHOTOGRAPHIC  IMAGE. 


This  salt  is  white,  its  taste  sulphurous,  not 
bitter  and  nauseous  as  that  of  sodium  thio- 
sulphate  (hyposulphite)."^  It  dissolves  in  4 
parts  of  cold  water  and  its  weight  of  boiling 
water.  The  anhydrous  compound  dissolves 
in  7.07  parts  of  water  at  0^  C,  in  3.35  parts 
of  water  at  15°  C,  and  2  parts  of  boiling 
water.  All  these  solutions  are  alkaline. 
They  dissolve  silver  chloride  and  bromide 
forming  double  salts,  which  can  be  employed 
for  silvering.  For  this  purpose  a  strong 
solution  of  silver  nitrate  is  gradually  added 
to  another  of  acid  sodium  sulphite  (bisulphite) 
until  the  precipitate  dissolves  with  difficulty, 
but  dissolves.  This  is  a  very  good  and  indus- 
trial process,  for  it  permits  one  to  obtain  a 
thicker  silver  deposit  than  by  most  of  the 
other  compounds.  Roseleur  gives  the  follow- 
ing proportion  :  1  AgNOs :  6  NagSOa. 

The  silver  solution  may  also  be  used  for  the 
intensification  of  negatives  previously  treated 
by  mercuric  chloride. 

*  These  two  salts  are  easily  distinguished  from  each 
other  by  adding  to  their  solution  a  small  quantity  of 
sulphuric  acid,  or  any  other  one,  sulphur  being  set  free 
if  the  salt  is  a  thiosulphate.  The  solution  of  the  sulphite 
remains  clear.   Both  evolve  sulphur  dioxide. 


CHEMIS  TR  Y  AND  BEHA  VIOR,  &c.  35 


Normal  sodium  sulphite  eitlier  in  crystals 
or  in  solution  absorbs  oxygen  from  the  air, 
being  gradually  transformed  into  sulphate. 

With  the  exception  of  carbonic,  hydrocyanic 
and  boric  acid,  the  hydracids,  sulphuric  acid, 
formic  and  citric  acids  decompose  it  evolving 
sulphur  dioxide  by  uniting  to  sodium.  Nitric 
acid  converts  it  into  sulphate  with  formation 
of  nitrous  fumes,  NO2. 

Sodium  sulphite  is  employed  as  an  anti- 
chlore  and  to  destroy  ferments. 

In  photography  it  is  employed  :  1st,  to  avoid 
the  rapid  oxidation  of  the  reagent  resulting 
from  its  absorption  of  the  atmospheric  oxy- 
gen :  the  sulphite  having  a  greater  affinity  for 
oxygen  than  the  reagents,  takes  it  up  from  the 
air,  so  that  the  oxidation  of  the  developer  only 
results  from  the  nascent  oxygen  dissociated 
during  the  development ;  and,  2nd,  to  prevent 
the  dyeing  of  the  film  by  its  deoxidizing 
action ;  or,  what  is  more  generally  admitted, 
by  causing  the  formation  of  an  incolorous  com- 
pound of  the  dye  with  the  hydrogen  liberated 
from  the  elements  of  water,  thus  : 


36  THE  PHOTOGRAPHIC  IMAGE. 


For  keeping,  the  developers  are  best  pre- 
pared with  the  hydrogen  or  acid  sodium  sul- 
phite (bisulphite),  NaHSOs,  whereby  the 
oxygen  does  not  act  on  the  sodium  salt,  but  on 
the  sulphurous  acid  which  is  converted  into 
sulphuric  acid.  The  acid  then  acts  on  the 
sodium  sulphite,  liberating  sulphurous  acid 
which  in  its  turn  undergoes  a  similar  change, 
thus : 

2  NaHSOs+O^H^SO.+Na^SOs 
and  Na2S03+H2S04=Na2S04+H2S03,  etc. 

Sodium  sulphite  can  exalt  the  reductive 
properties  of  pyrogallol  sufficiently  to  develop 
the  latent  image.  The  development  is  slow 
and  yields  clear  negatives.  The  sulphites  also 
prevent  fogging  when  added  to  hydroquinone. 

This  energetic  action  imparted  to  the  de- 
veloper does  not  depend  from  the  carbonate 
which  the  commercial  sulphite  always  con- 
tains, for  the  chemically  pure  salt  behaves  in 
the  same  manner. 

According  to  Captain  Abney,  sodium  sul- 
phite forms  a  very  oxidizable  compound  with 
pyrogallol.  This  and  the  alkaline  reaction  of 
the  salt  account  for  the  phenomenon. 


CHEMISTRY  AND  BEHAVIOR,  &c. 


37 


Sodium  sulphite  does  not  act  so  with  hydro- 
quinone.  The  mixture  is  incapable  of  effect- 
ing the  development  of  the  image.  But  it  does 
with  eikonogen,  probably  by  preventing  this 
salt  to  exhaust  its  reductive  action  by  absorb- 
ing oxygen  from  the  air,  for  which  it  possesses 
an  exceedingly  great  affinity. 

From  4  to  5  parts  of  sodium  sulphite  for  1 
of  pyrogallol,  3  to  4  for  1  of  hydroquinone,  6 
to  7  for  1  of  eikonogen  are  sufficient  to  check 
for  a  certain  period,  long  enough  for  the 
exigencies  of  the  development,  the  oxidation 
of  the  reagents  in  contact  with  the  air. 

Eeady-made  developers  are  necessarily  com- 
pounded with  larger  proportions  of  sulphite  on 
account  of  the  presence  of  the  alkalies. 

Many  acids  have  been  recommended  to 
evolve  sulphurous  acid  from  the  sulphite  in 
order  to  keep  the  plain  solutions  of  pyrogallol 
and  hydroquinone  for  a  long  time.  Such  are 
citric,  oxalic,  formic,  nitric,  sulphuric  acids, 
etc.  The  two  former  form  with  the  base  of  the 
sulphite  compounds  which  act  as  restrainers; 
the  formate  exerts  a  certain  reductive  action ; 
as  to  the  sulphate   and   nitrate   they  are 


38 


THE  PHOTOGRAPHIC  IMAGE. 


inert.*  Sulphuric  and  nitric  acid  are  therefore 
recommended.  From  2  to  4  per  100  of  sodium 
sulphite  are  sufficient  for  the  purpose  in  ques- 
tion. 

Hydeogen  or  Acid  Sodium  Sulphite  (Bi- 
sulphite), NaHSOs-  This  salt  is  white  and 
evolves  the  smell  of  sulphur  dioxide.  "When 
anhydrous  it  is  termed  metabisulphite.  It 
attracts  oxygen  from  the  air  more  rapidly  than 
the  normal  salt.  When  used  in  the  developing 
solution  it  is  converted  into  the  normal  salt 
by  the  alkaline  carbonates : 

2  NaHS03+Na2C03=2  Na2S03+C02+HA 

There  is  in  the  market  a  solution  sold  under 
the  name  of  acid  sulphite  marking  30°  Baume. 
It  consists  of  bisulphite  with  sulphurous  acid 
in  great  excess. 

It  is  employed  for  keeping  the  solutions  of 
pyrogallol,  hydroquinone,  etc.,  free  from  oxida- 
tion, and  as  a  clearing  agent  in  the  thiosul- 
phate  fixing  bath. 

What  is,  besides  preventing  the  oxidation  of 

*  According  to  some  authors  the  sulphates  act  a» 
feeble  restrainers. 


CHE  MIS  TR  Y  AND  BEHA  VIOR,  <&c.  39 


the  reagent  by  the  atmospheric  oxygen,  the 
action  of  sodium  sulphite  in  the  development? 

When  in  great  excess  it  retards  the  develop- 
ment :  this  has  been  observed  by  all  the 
operators.  And  what  is  important,  Mr.  H. 
Reeb  has  constated  that  the  reduced  silver  is 
black  when  the  image  is  developed  by  hydro- 
quinone  compounded  with  a  small  dose  of  sul- 
phite, while  it  is  white  or  gray-white  if  the 
dose  is  large. 

Hence,  says  Mr.  Reeb,  sodium  sulphite  in 
great  excess  retards  the  formation  of  the  silver 
deposit  and  whitens  it. 

A  solution  of  sodium  sulphite  at  10  per  100 
is  sufficiently  concentrated  to  dissolve  silver 
bromide. 


RESTRAINERS— ACCELERATORS. 

As  the  name  indicates  it,  the  restrainers 
retard  the  development  of  the  latent  image, 
but  does  not  stop  it  entirely  unless  employed 
in  very  large  doses.  They  act,  therefore,  in 
opposition  to  the  alkalies  which  increase  the 
reductive  power  of  certain  reagents  and,  as 


40 


THE  PHOTOGRAPHIC  IMAGE, 


before  explained,  predispose  the  silver  salts  to 
be  acted  upon  by  the  developer. 

The  action  of  the  restrainers  is  necessarily  in 
proportion  much  greater  on  the  parts  the  least 
impressed  than  on  the  others,  the  high  lights, 
for  in  these  the  silver  salt  having  a  great  tend- 
ency to  dissociation,  the  reductive  action  will 
dominate  while  it  will  be  feeble  on  the  former, 
that  is,  the  half  lights  or  details  in  the 
shadows.  This  explains  their  use  in  cases  of 
over  exposures  and  whenever  it  is  useful  to 
increase  the  contrasts  in  the  image.  Other 
means  are  at  our  disposal  for  the  same  pur- 
poses, but  these  are  often  of  a  great  utility. 

Various  salts  are  employed  as  restrainers  or 
regulators.  Such  are  the  alkaline  haloids, 
NaCl,  KI,  KB2,  the  citrates,  sodium  biborate 
(borax),  the  picrates,  etc.  The  two  latter  are 
very  energetic,  the  picrates  especially. 

Potassium  bromide  is  usually  employed. 
Its  mode  of  action  is  not  well  know.  It  very 
probably  acts  by  its  tendency  to  form  a  double 
salt  with  nascent  silver,  KAgBrg,  upon  which 
the  developer  does  not  act  with  energy.  It  is 
well  known  that  the  corresponding  iodide  salt 
is  insensitive  to  light. 


CHEMISTRY  AND  BEHAVIOR,  &c.  41 


The  action  of  the  other  alkaline  haloids  is 
similar. 

Certain  organic  substances,  sugar,  glycerine, 
gelatine,  etc.,  act  also  as  restrainers  either  in 
virtue  of  their  viscosity  or  their  tendency  to 
form  feeble  compounds  with  silver  (Meldola). 
These  substances,  among  which  albumen 
should  be  included,  are  termed  physical  re- 
strainers,  to  distinguish  them  from  those,  the 
chemical  restrainers^  which  are  capable  of  com- 
bining with  silver  in  the  nascent  state. 

The  action  of  the  physical  restrainers  is 
feeble,  but  sufficient  to  prevent  fogging  with 
developers  compounded  with  the  alkaline  car- 
bonates in  normal  doses. 

"With  the  ammonia-pyrogallol  developer  a 
restrainer,  potassium  bromide,  is  indispensable 
to  obtain  clear  negatives.  For  normal  ex- 
posure-times the  proportion  may  be  from  3  to 
5  for  1000  parts  of  water  with  5  parts  of  pyro- 
gallol  and  from  6  to  8  parts  (a  large  dose)  of 
concentrated  aqueous  ammonia.  In  this 
formula  the  quantity  of  restrainer  suffices 
for  the  purpose  in  question,  but  not  to  cause  a 
marked  restraining  action. 

The  caustic  alkalies  KOH,  NaOH,  are  sel- 


42 


THE  PHOTOGRAPHIC  IMAGE. 


dom  employed  with  pyrogallol ;  tliej  act 
too  energetically  with  it.  "When  used  with 
hydroquinone  and  eikonogen  —  the  latter 
especially — a  small  quantity  of  potassium 
bromide  is  quite  advantageous  to  keep  the 
shadows  clear. 

With  the  carbonates,  K2CO3,  NaaCOs,  the 
restrainers  are  employed  only  in  special  cir- 
cumstances and  always  in  very  small  quantities; 
3  for  1000  is  a  large  dose  in  case  of  over 
exposure. 

To  resume,  the  restrainers  are  employed : 

1st.  To  prevent  fogging  hy  checking  the  too 
energetic  action  of  the  caustic  alkalies  ; 

2nd.  In  cases  of  over-exposures  to  prevent  the 
image  of  developing  rapidly  in  all  its  parts  and, 
therefore^  to  allow  the  lights  and  half-lights  to 
appear  successively  in  keeping  their  relative  values; 

3rd.  To  obtain  contrasts  ivhen  the  subjects  ar& 
greys  uniform  ; 

4th.  To  keep  the  lines  clear  when  photograph- 
ing engravings f  pen  and  ink  draivings,  etc. 

With  extra  rapid  plates,  the  restrainers  are 
always  useful  to  keep  the  shadows  free  from 
fog. 


CHEMISTRY  AND  BEHAVIOR,  &g.  43 


There  are  two  compounds  which  effectually 
cause  a  more  rapid  development :  sodium 
thiosulphate  (hyposulphite)  and  a  mixture  of 
the  same  salt  with  mercuric  chloride.  The 
former  is  employed  with  the  ferrous  oxalate 
developer,  the  other  with  eikonogen. 

The  chemical  action  giving  rise  to  the  accel- 
eration, when  sodium  thiosulphate  is  added  to 
the  developing  solution  of  ferrous  oxalate  con- 
sists, says  Capt.  Abney,  who  introduced  this 
accelerator  in  1880,  to  convert  the  ferric 
bromide  formed  during  the  reduction  of  the 
silver  salt  into  sodium  bromide  whose  restrain- 
ing action  is  less  energetic  ;  thus,  according  to 
Abney : 

2  Na2SA+Fe2Br6=2  'FqBv,+^  NaBr+ 
Na2S406 

then  Na2S203+FeBr2=reS203+2  NaBr. 

Dr.  Hermann  W.  Yogel  attributes  the  accel- 
eration to  the  hyposulphite  of  iron. 

In  reality  the  cause  is  not  well  ascertained, 
for  a  much  more  complicated  chemical  change 
occurs  :  the  ferric  oxalate  resulting  from  the 
oxidation  of  the  ferrous  salt,  which  acts  as  an 
enegetic  restrainer,  is  deoxidized  with  formation 


44  THE  PHOTOGRAPHIC  IMAGE. 


of  sodium  tetratliionate  and  sodium  oxalate  : 

1^62(0204)3  +  2  Na^S^Os  =  2  reC204  +  NaA06+ 
Na2C204.  (Meldola.) 

As  to  the  action  of  the  mixture  of  sodium 
thiosulphate  and  mercuric  chloride  in  the 
eikonogen  developer,  we  do  not  understand  it. 
The  mercuric  salt  is  converted  into  sulphide 
in  presence  of  sodium  thiosulphate  : 

HgCl2+Na2S203+H20 = HgS+2  HCl+Na2S04. 

There  is  no  thiosulphate  of  mercury  and  no 
sulphite. 

According  to  "Wolf  and  Lenhard  turpentine 
oil  acts  as  an  accelerator  with  hydroquinone ; 
6  or  6  drops  added  to  100  cubic  centimeters  of 
the  developing  solution  suffice. 

Dr.  Eder  states  that  the  addition  of  a  tinc- 
ture of  iodine  compounded  thus  — 

Iodine     ...     1  part, 
Alcohol  .  .    50  parts, 

Water     .     .     .    50  *' 

acts  in  the  same  manner  with  hydroquinone. 
"  From  3  to  6  parts  added  to  480  parts  of  the 
developer  cause  the  image  to  appear  instanta- 
neously." *'  The  contrasts  are  softened.  When 


CHEMISTRY  AND  BEHAVIOR,  do. 


45 


the  exposure  is  instantaneous,  one  obtains  a 
weak  cliche.  Four  parts  added  to  an  eiko- 
nogen  developer  have  a  less  marked  action, 
but  the  image  is  clearer." 

In  our  practice  we  found  that  iodine  acted 
as  a  restrainer. 


summaey  of  the  actions  of  the  chemicals 
Employed  to  Compound  a  Developee. 

Pjrogallol,  hydroquinone,  eikonogen  and 
ferrous  oxalate  are  the  agents  which,  in  a 
developing  solution,  effect  the  reduction  of  the 
silver  salts  acted  on  by  light  and,  therefore, 
the  development  of  the  latent  image.  As  a 
consequence,  they  tend  to  produce  intensity  and 
contrasts. 

With  the  exception  of  ferrous  oxalate  and 
certain  organic  ferrous  salts  which  are  capable 
per  se  of  developing  the  image,  the  reductive 
property  of  the  other  reagents  is  not  generally 
sufficiently  powerful  to  effect  it  unless  the 
image  be  strongly  impressed. 


46 


THE  PHOTOGRAPHIC  IMAGE. 


The  reductive  property  of  the  developing 
solutions  compounded  with  the  reagents  in 
question  is  exalted  by  the  alkalies,  the  action 
being  more  effective  with  pyrogallol  which 
unites  to  the  bases  forming  a  py'rogallate, 
so-called,  oxidizing  very  rapidly. 

The  alkalies  exert  also  a  very  important 
action  without  which  the  reducing  influence  of 
the  reagent  would  not  be  suflQcient  to  develop 
in  time  the  weak  impression  formed  during  the 
period  of  short  exposures :  they  act  on  the 
whole  photo-film,  causing  the  constitutive 
elements  of  the  silver  haloids  to  be  easily  dis- 
sociated by  the  developer.  Hence,  tJiey  tend  to 
produce  softness  and  harmony,  and  fogging  hy 
excess. 

The  sulphites  having  for  oxygen  a  great 
affinity,  prevent  the  oxidation  of  the  reagents 
by  absorption  of  the  atmospheric  oxygen, 
without,  however,  impairing  their  reductive 
property  or,  at  least,  to  an  extent  without 
importance,  if  not  employed  in  great  exess. 

Practically,  the  sulphites  prevent  yellow  fog  so 
long  as  the  reagent  is  not  much  oxidized,  when  it 
forms  a  compound  j^ossessing  tinctorial  properties. 


CHEMIS  TR  Y  AND  BEHA  VIOR,  &c .  47 


Tlie  restrainers  act  in  opposition  to  the 
alkalies  and  necessarily  more  effectively  on  the 
half  tints  than  on  the  high  lights  or  parts  the 
most  strongly  impressed.  Therefore,  they  tend 
to  produce  contrasts  and  to  prevent  fogging. 

Potassium  bromide  is  usually  employed. 
Its  action  is  energetic.  In  a  normal  developer 
1  per  500  is  a  large  dose  for  correct  exposures. 

Potassium  ferrocyanate  is  a  weak  restrainer. 
It  is  especially  useful  to  obtain  clear  cliches 
when  the  plate  should  be  treated  with  large 
doses  of  alkalies,  or  first  treated  by  the  same, 
then  gradually  adding  pyrogallol,  or  other 
reagents.    2  per  100  is  an  ordinary  dose. 

We  have,  now,  little  to  say  about  the  appli- 
cations of  the  reagents.  They  will  be  ex- 
plained in  extenso  under  the  proper  headings. 
We  have,  however,  to  call  the  attention  of  the 
student  to  the  following  facts  which  explain 
the  various  modifications  made  in  the  develop- 
ing mixture  to  meet  every  case  of  exposure 
and,  especially,  the  lighting  of  the  subject. 

A  given  quantity  of  reducing  agent,  pyro- 
gallol, for  example,  can  reduce  only  a  certain 


48  THE  PHOTOGRAPHIC  IMAGE. 


amount  of  the  silver  salt  forming  the  photo- 
film  and,  as  a  consequence,  produces  a  propor- 
tionate opacity,  since  the  reduction  of  the 
silver-film  commences  from  the  surface. 

Hence,  if  to  a  solution  of  an  alkali  a  small 
dose  of  pyrogallol  be  added,  the  whole  silver- 
film  being  acted  on,  the  image  gradually 
appears  in  all  its  parts,  owing  to  the  secondary 
action  of  the  alkali,  without,  however,  assum- 
ing much  intensity  on  account  of  the  weakness 
of  the  reducing  solution,  and  its  action  being 
divided  all  over  the  film. 

Therefore,  the  parts  the  most  impressed  by 
the  luminous  influence — the  high  lights  of  the 
image — although  first  making  their  appear- 
ance, as  it  should  be  expected,  remains  weak, 
while  the  other  parts — the  details  or  half  tints 
— develop  in  taking  a  greater  intensity  in 
relation  to  the  former.  In  fact,  should  the 
exposure  have  been  lengthened  the  whole 
image  would  appear  at  once,  so  to  say,  and 
remain  stationary. 

But  if  the  dose  of  pyrogallol  be  increased  to 
the  maximum  so  as  to  subdue  or  partly  annul 
the  special  action  of  the  alkali,  then  the  devel- 
opment proceeds  as  before,  but  the  high  lights 


CHEMISTRY  AND  BEHAVIOR,  (&c.  49 


go  on  rapidly  intensifying  before  the  details 
appear  or  assume  a  proportionate  opacity. 
The  result  is,  therefore,  a  cliche  too  intense 
in  the  lights  and,  consequently,  yielding  harsh 
positive  impressions. 

On  these  actions  is  based  the  modus 
operandi  of  the  development. 


CHAPTER  ii. 


The  Daek-eoom  iLLUMmATioN. 


We  will  not  describe  the  dark  room.  Any 
arrangement  is  good.  The  main  point  is  that 
the  light  does  not  impress  the  photo-films. 

In  working  the  wet  and  dry  collodion  plates 
— except,  however,  those  prepared  with  silver 
bromide  only — the  light  from  a  petroleum  lamp 
transmitted  through  an  orange-colored  glass 
backed  by  a  ground  plate  is  safe  at  the  distance 
of  about  one  metre,  but  not  when  preparing  or 
developing  gelatine  plates  which  are  sensitive 
to  the  green  rays  and  even  to  the  red  when 
they  are  very  rapid. 

Generally,  glass  plates  stained  red  in  the 
mass  by  copper  are  preferred  in  such  a  case. 
Most  of  the  dry  plate  lanterns  are  made  with 
these  ruby  plates. 


THE  DARK-ROOM  IL L UMINA TION.  51 


Paper  dyed  with  clirysoidine,  and  glass 
plates  coated  with  gelatine  colored  with  this 
substance  may  be  employed  as  substitutes  for 
red-stained  plates.  The  gelatine  mixture  is 
compounded  thus  : 

Gelatine   8  parts, 

Chrysoidine     .      .      .      .  1  part. 

Glycerine  1  *' 

Water   30  parts; 

when  dissolved  add  a  warm  solution  of 

Chrome  alum  ....    1  part, 

Water   10  parts. 

Coat  the  plate  while  the  solution  is  warm. 
When  solidified  the  gelatine  is  insoluble. 

A  good,  red-shellac  varnish  or  thick,  plain 
collodion  colored  per  cent  with  two  parts  of 
chrysoidine  transmits  also  a  safe  red  light. 

Manchester  brown  is  equally  an  excellent 
dye  for  the  purpose  in  question.  It  transmits 
the  red  light  only. 

If  one  objects  to  the  red  light  as  being  tire- 
some to  the  eyes,  a  light-red  ground-glass 
superposed  on  a  green  one,  or  a  combination 
of  a  ground  deep  orange-colored  glass-plate 
and  a  yellow-green  one  can  be  used;  or  a 
ground  plate  coated  on  the  back  with  a  varnish 


52 


THE  PHOTOGRAPHIC  IMAGE. 


or  collodion  deeply  colored  with  fluorescein.* 

To  develop  orthochromatic  plates  a  red 
light  only  is  safe,  and  not  much  of  it  when  the 
plates  are  red  sensitive.  According  to  Mr. 
Fred.  Ives  "  a  dark  yellow-green  glass  is  the 
safest  light  to  develop  by."  t 

It  is  always  a  good  precaution  to  test  the 
actinism  of  the  light.  For  that  purpose  cover 
a  photo-plate  with  an  opaque  material,  a  black 
cardboard  more  than  twice  longer  than  the 
plate  and  with  an  opening  cut  in  the  middle  of 
it.  Now,  uncovering  the  opening  previously 
placed  on  the  lower  part  of  the  plate,  expose 
to  the  light  at  a  distance  of  five  centimeters 
for,  say,  thirty  or  forty  seconds ;  then  repeat 
the  operation  by  uncovering  another  part  of 
the  plate  and  exposing  for  the  same  period  at 
a  distance  of  one  decimetre,  and  proceed  by 
successively  increasing  the  distance  to  two, 


*  Fluorescein  is  almost  insoluble  in  water,  soluble 
in  alcohol,  which  then  exhibits  a  beautiful,  green 
fluorescense.  The  solution  in  ether  is  yellow  and 
not  fluorescent.  Fluorescein  absorbs  all  the  rays  of 
light  but  the  yellow  and  red.  The  diluted  solution  gives 
an  absorption  band  in  the  green. 

f  Cathedral  green-glass  backed  with  an  orange-colored 
ground -plate. 


THE  DARK-ROOM  ILL  UMINA  TION.  53 


then  to  four  decimetres  :  by  developing  yon 
will  ascertain  whether  the  light  has  on  the  film 
any  actinic  action  or  not  and,  if  it  has,  at  what 
distance  from  it  it  is  safe  to  operate. 

Many  forms  of  lanterns  have  been  devised 
for  lighting  the  dark  room.  We  advise  the 
reader  to  select  a  very  large  one  :  if  the  light  is 
safe,  it  can  be  used  in  great  quantities.  Car- 
butt's  Ilultum  in  Parvo  plate  lantern  is 
excellent  and  serves  for  several  purposes. 


CHAPTER  III. 


The  Exposure-time. 


Although  the  gelatine  plates  allow  on 
account  of  the  elasticity  of  the  developing 
methods  a  certain  latitude  in  the  exposure-time, 
one  should  avoid  to  over  expose  in  excess  and 
most  decidedly  to  under  expose.  Hence,  when 
exposing  by  the  drop  shutter  the  largest 
diaphragm  consistent  with  good  definitions 
must  be  employed  and  the  speed  of  the  drop 
shutter  as  slow  as  the  scene  or  the  distance 
permits. 

The  exposure-times  are  classified  by  photo- 
graphers as  normal,  over  and  under  exposures^ 
which  latter  means  a  short  exposure,  for  a  plate 
which  has  been  really  under  exposed  will 
never  yield  but  a  bad  white  and  black  image. 


THE  EXPOS  URE  TIME. 


55 


The  normal  exposure,  as  the  name  indicates 
it,  is  correct,  or  more  properly  speaking,  suffi- 
cient. In  developing,  the  image  gradually 
appears,  the  high  lights  coming  out  first,  then, 
and  soon  after,  the  details  in  the  shadows, 
while  if  the  plate  is  over  exposed,  the  image 
flashes  out,  the  details  appearing  almost  simul- 
taneously with  the  high  lights,  the  pictures 
being,  therefore,  deficient  in  contrasts,  without 
vigor  if  the  development  is  not  regulated.  On 
the  other  hand  when  the  exposure  is  short  to 
a  certain  extent,  the  lights  develop  slowly,  the 
half  tints  hang  back,  and  no  matter  how  the 
development  is  managed,  the  picture  is  seldom 
a  good  and  complete  one  :  instantaneous  views, 
for  example,  unless  taken  with  a  large  dia- 
phragm to  place  the  principal  subject  well  in 
focus  and  more  or  less  sacrificing  the  rest. 

From  what  precedes,  it  follows  that : 

1st.  Normal  exposure-time  leads  to  obtain 
photographs  fall  of  details  or  half  tones,  softness  or 
vigor  being  obtained  at  will  by  the  development 

2nd.  By  short  exposure-times  greater  contrasts 
and  brilliancy  are  produced  at  the  expense  of  the 
delicate  details  in  the  shadoivs,  and  if  one  forces 


5G  THE  PHOTOGRAPHIC  IMAGE. 


the  development  to  bring  them  out^  then  the  half 
tones  in  the  high  lights  will  he  blocked  up  ; 

3rd.  Over  exposure-time  produces  softness  and, 
by  excess y  flatness,  which  latter  can  be  remedied  by 
the  development.  However ,  the  lights  are  generally 
solarized,  that  is,  more  or  less  devoid  of  half  tints, 
ami  the  whole  picture  liable  to  fog  ; 

4tli.  By  under  exposure-time — real  under  ex- 
posure— no  good  pictures  can  be  obtained  ;  they  are 
harsh,  white  and  black. 

It  must  not  be  inferred  from  these  state- 
ments that  an  exact  exposure-time  is  a  sine  qua 
non.  There  is,  on  the  contrary,  a  certain 
latitude,  as  said  above,  so  much  the  greater  as 
the  plates  are  less  sensitive;  and  whenever 
there  is  not  a  great  excess  one  way  or  the 
other,  it  is  always  possible  to  obtain  negative 
cliches  technically  good. 

A  normal  exposure-time  may  be  defined  the 
exposure  which,  with  a  given  brand  of  plates 
developed  by  the  following  developer  yields  a 
perfect  picture,  provided  the  subject  be 
lighted  without  great  contrasts. 


THE  EXPOSURE  TIME. 


57 


Sodium  sulphite,  . 
Sodium  carbonate 
Potassium  carbonate 


3. 


parts,* 


2. 


1. 


part, 


Pyrogallol  .  .  .  .  0.5  " 
Potassium  bromide  .  0.01  ** 
Water,       .       .       .       120.  parts. 

The  normal  exposure-time  varies,  to  a  cer- 
tain extent,  with  the  energy  of  the  reductive 
action  of  the  developer  and  its  temperature. 

The  above  definition  applies  only  to  a 
solution  of  pyrogallol  at  16°  C.  (60°  Fahr.)t 
compounded  as  in  the  above  formula. 

To  study  the  effects  of  various  periods  of 
exposure,  let  us  make  the  experiment  follow- 
ing: 

Subject — a  spring  landscape  with  foliages  in 
the  foreground  ;  lighting — fair ;  lens — a  Dar- 

•  We  give  all  the  formulas  in  parts ;  grains  or  grams 
for  the  solids  ;  minims  or  cubic  centimetres  for  the 
liquids. 

t  The  influence  of  heat  on  the  development  was  dem- 
onstrated in  1862,  by  Dr.  John  W.  Draper,  then  president 
of  the  American  Photographical  Society,  A  dry  collo- 
dion plate  was  treated  by  "hot  development"  and 
another  by  a  developer  at  40°  F. ;  the  image  in  the  former 
case  came  out  rapidly  with  good  details,  while  the  other 
slowly  developed,  the  light  being  intensified  before  the 
details  were  visible.  The  relation  between  the  tempera- 
ture and  the  developing  time  is  about  as  follows  ;  at  10° 
0.,  3  minutes ;  at  20°  0.,  2  minutes ;  at  30°  0.,  1  minute. 


58  THE  PHO'tOGRAPHlC  IMAGE. 


lot's  rectilinear  30  centimetres  focus ;  stop  32 ; 
plate — a  Carbutt's  B  sensitometre  20.  We  first 
draw  the  lid  one-fourth  off  and  expose  3 
seconds;  then,  drawing  the  lid  one-fourth 
more  we  expose  2  seconds  and  thus  proceed 
exposing  2  seconds  and,  lastly,  1  second.  The 
exposure-times  are  therefore  thus  graduated  : 
8,^^  5/'  d/'  1/' 

Now,  nearly  as  soon  as  the  plate  is  immersed 
in  the  above  developing  solution,  the  first 
fourth  of  the  image,  that  corresponding  to  8 
seconds  exposure,  appears  in  all  its  details  and 
rapidly  intensifies,  the  whole  being  veiled  by  a 
superficial  reduction ;  the  second  fourth  will 
appear  very  soon  after  and  give  a  picture 
deficient  in  contrasts,  while  the  next  fourth 
exposed  for  3  seconds  being  well  exposed,  will 
develop  regularly,  the  high  lights,  half  lights, 
and  details  in  the  shadows  appearing  one  after 
the  other  at  short  intervals  and  intensifying 
with  their  relative  value.  As  to  the  part 
exposed  only  during  1  second,  the  high  lights 
will  appear  probably  n©t  before  a  minute 
or  more,  and  intensify  much  before  the  details 
are  visible. 

Therefore,  in  this  example,  8  seconds  is  an 


THE  EXPOSURE  TIME. 


59 


exaggerated  over  exposure-time;  5  seconds  is 
also  an  over  exposure-time :  but,  in  both  cases, 
by  properly  managing  the  development,  still 
a  fair  picture  can  be  obtained.  3  seconds  is 
the  so-called  normal  exposure  and  there  will 
be  no  trouble  to  obtain  a  perfect  picture  if 
the  lighting  of  the  subject  is  good,  as  we  sup- 
pose it :  we  have  only  to  allow  the  development 
to  proceed.  The  1-second  is  no  doubt  too  short 
an  exposure,  maybe  not  past  remedy  if  the 
developer  is  compounded  with  excetis  of  alkali, 
little  pyrogallol,  and  so  forth,  a,tj  it  will  be 
further  on  explained. 

The  exposure-time  for  portraits  in  a  photo- 
graphic studio  is  about  as  follows  : 

Stop  |,*  plates  sensitometre  25  c,  2^  seconds, 
**         '*  "         23  c,  31 

"         "  *'         20  c.,  5 

[See  Note,  page  60.] 

*  The  figures  | ,  indicate  the  diameter  of  the  aper- 
ture of  the  stops  in  relation  to  the  equivalent  focus  of 
the  lens,  thus:  f  means  an  aperture  of  one-fourth  the 
focus ;  I  that  of  one-eighth  the  length  of  the  focus,  &c. 
Practically  a  lens  requires  about  the  same  exposure-time 
as  another  of  the  same  construction  similarly  stopped 
down,  that  is,  in  the  same  proportion  relatively  to  the 
focal  length;  and,  as  the  quantity  of  light  passing 
through  apertures  increases  or  diminishes  with  the 
square  of  the  difference  between  the  apertures  it  follows 


THE  PHOTOGRAPHIC  IMAGE. 


For  out-door  works,  landscapes : 

Stop    ,  platos  sensitometre  25  c,  1|  seconds, 
"  **         23  c,  2  «* 

«'         «*  "         20c.,2|  '* 

"         **  "         16  c,  3i  to  4  seconds. 

[)See  Note.] 

Note. — By  full  day-light,  i.  e.,  from  10  to  3  o'clock  in 
April,  May,  June,  July,  and  August;  then  the  ex- 
posure-time increases  as  the  sun  is  lower  on  the  horizon. 
For  extra  rapid  gelatine  plates,  one-third  less  than  for 
plates  sensitometre  25  c.  Lens  k.r.,  equivalent  focus  32 
centimetres. 

The  exposure-time  varies  very  mucli  for 
landscapes,  thus :  the  exposure  being  1  second 
for  a  panoramic  view,  will  be,  say,  3  seconds 
with  foliages  in  the  foreground,  6  seconds  and 
more  if  the  foliage  is  dark  green  and  badly 
lighted,  &c. 


that  the  exposure-time  varies  in  the  same  ratio,  thus :  if, 
say,  one  second  is  the  exposure-time  required  with  J,  it 
should  be  increased  four  times  with  i  which  is  twice  a 
smaller  aperture,  sixteen  seconds  with  which  is  four 
times  smaller  than  f,  sixty-four  seconds  with  f^.  &c. 
However,  in  practice  it  is  found  that  the  exposure-time 
does  not  so  increase,  being  less. 

In  our  practice  we  use  for  rapid  exposures  by  the 
drop  shutter,  and  for  landscapes  ^  or  as  the 
smallest  stop. 

For  general  use,  Carbutt's  plates  sensitometre  25  are 
recommended. 


THE  EXPOSURE  TIME. 


61 


As  it  lias  been  already  explained  in  the  begin- 
ning of  this  work,*  a  very  curious  series  of 
phenomena  occurs  during  the  exposure-time. 
It  seems  that  the  longer  the  exposure  the 
more  opaque  should  be  the  blacks  of  the 
cliche,  that  is,  the  parts  corresponding  to  the 
whites  of  the  model ;  but  it  is  not  so.  After 
a  certain  period  light  destroys  what  it  has 
done,  the  blacks  become  less  intense,  then 
more  and  more  transparent;  they  are  solar- 
ized. The  degree  of  intensity  obtained  by  the 
development  does  not,  therefore,  coincide  with 
the  time  of  isolation  beyond  a  certain  limit; 
and,  as  the  action  of  the  lights  reflected  from 
the  model  varies  with  their  intensity,  it  should 
be  necessary  to  vary  the  exposure-time  for 
every  one  to  photograph  them  with  their  real 
value.  Of  course  this  is  practically  impos- 
sible; the  exposure-time  is  the  same  for  all 
the  parts  of  the  film.  How  shall  we  proceed, 
then,  specially  if  the  object  presents  great  con- 
trasts of  lights  and  shades,  etc.  ?  The  reader 
has  already  given  the  answer :  by  prolonging 

*  We  beg  to  be  forgiven  for  sometimes  repeating  over 
what  "we  have  already  explained.  Eepetitions  are  una- 
voidable in  a  work  specially  written  for  students. 


62 


TBE  PHOTOGRAPHIC  IMAGE. 


the  period  of  exposure  in  order  to  allow  the 
weak  lights  of  more  strongly  impressing  the 
photo-film.  But  then  an  unavoidable,  although 
less  objectionable,  defect  occurs — the  picture 
is  more  or  less  solarized,  and  the  most  deli- 
cate half-tints  in  the  high  lights  disappear. 

To  a  great  extent  this  may  be  prevented  by 
the  manner  of  conducting  the  development 
and,  more  effectually,  by  the  orthochromatic 
process. 

As  a  rule —  When  the  subject  is  st^^ongly  illum- 
inated and  shows  great  contrasts  of  lights  and 
shades,  the  exposure-time  should  he  increased  and, 
OjS  a  consequence,  shortened  when  the  lighting  is  too 
uniform,  the  subject  wanting  in  vigor  and  bril- 
liancy. 

Hence,  whenever  the  subject  is  lighted  by 
violent  contrasts  one  should  not  hesitate  to 
expose  three  to  four  times  longer  than  the 
so-called  normal  exposure  requires,  for  in  such 
cases  one  may  over  expose  without  exposing 
enough,  that  is,  without  reaching  that  peculiar 
period  observed  by  Janssen.  when  the  high 
lights  are  re-impressed. 

The  photo-film   so  impressed  should  be 


THE  EXPOSURE  TIME. 


63 


treated  by  a  weak  and  diluted  developer  as  it 
is  explained,  with  examples,  in  Part  11. 

To  determinate  a  priori  the  correct  expo- 
sure-time is  the  stumbling-stone  for  the 
student,  in  fact  it  depends  on  so  many  and 
various  conditions — the  actinism  of  the  light 
which  varies  with  the  season,  the  time  of  the 
day,  the  color  of  the  atmosphere  often  yellow- 
ish in  summer  and  autumn,  the  color  or 
ensemble  of  colors  of  the  object,  its  distance, 
kc. — that  even  the  experienced  photographer 
can  only  guess  it  approximatively. 

Many  photometres  have  been  devised  for 
the  pur]30se  in  question.  That  of  "Woodbury 
is  good  for  long  exposures  and  specially  for 
printing  by  the  carbon,  photoglyptic  and 
photo-engraving  processes  when  an  exposure 
of  a  few  seconds  more  or  less  have  but  little 
influence  on  the  result,  if  any  ;  but,  as  the 
quality  of  the  light  is  ascertained  by  the  color 
of  the  reduction  of  silver  chloride  compared  to 
another  one  printed  on  the  apparatus,  which 
it  is  not  easy  to  judge  well,  it  is  not  very 
reliable  for  exposing  rapid  photo-films. 


64. 


THE  PHOTOGRAPHIC  IMAGE. 


Fig.  717. 


Fig.  718. 


A  more  practical  pliotometre  is  that  devised 
by  Mr.  J.  Ducaudun,  of  Paris.  It  is  repre- 
sented in  the  figures  above.  To  use,  after 
having  taken  the  focus  and  placed  the  dia- 
phragm, the  sector,  consisting  of  three 
apertures,  is  applied  on  the  ground-glass,  in 
such  a  manner  as  the  largest  opening  corre- 
sponds to  the  mean  lighting  of  the  subject. 
Then  one  turns  the  knob  placed  in  the  centre 
of  the  apparatus  until  the  three  luminous 
points  become  almost  undiscernible.  Now 
the  required  exposure  time  will  be  found  by 
the  figure  opposite  to  the  lettei  visible  in  the 
circular  aperture  at  the  back. 


These  are  engenious  apparatus.  They  can 
render  real  services  but  can  not  replace  the 


THE  EXPOSURE  TIME. 


65 


experience  one  acquires  bj  practising  :  noth- 
ing is  meclianical  in  photography.  If  the 
photo-fihus  were  all  of  the  same  sensitiveness, 
if  the  subjects  were  all  alike,  of  the  same 
color  and  normally  lighted,  of  course  they 
would  be  invaluable  :  but  it  is  not  so ;  the 
exposure-time  is  not  only  subordinate  to  the 
actinism  of  the  light  but  also  to  ali  these 
influences,  and  cannot  be  determinated  by  any 
photometre,  however  perfect  it  is.  It  is  there- 
fore a  study  to  make.  The  difficulties  are  not, 
however,  as  great  as  they  may  seem  to  the 
reader.  By  well-conducted  experiments  they 
soon  will  be  mastered. 

The  exposure-time  for  gelatine  plates  does 
not  exceed  twenty-five  to  thirty  seconds,  ex- 
cept in  some  special  cases,  as  photographing 
interiors,  for  example,  when  it  may  extend 
to  several  minutes. 

To  count  seconds  in  the  glass-house  nothing 
is  more  convenient  than  a  pendulum.  A  lead 
ball  fixed  at  the  end  of  a  wire  or  a  string 
one  metre  long  oscillates  very  nearly  in  one 
second.* 

*  The  time  of  oscillation  for  the  same  pendulum  varies 


66 


THE  PHOTOGRAPHIC  IMAGE. 


An  empirical  manner  of  counting  seconds 
out  doors  is  to  rapidly  pronounce  four  syllables 
— plio  -  to  -  gra  - phy ,  for  example — wliicli  re- 
quire the  period  of  one  second  or  thereabout. 
For  an  exposure  of  four  seconds,  these  syllables 
should  be  four  times  repeated  ivitliout  interrup- 
tion. Examples :  for  one  second,  in  uncapping 
the  lens  say  plio,  &c.,  and  cap  the  lens  in 
pronouncing  pho  again;  for  half  a  second, 
uncap  in  pronouncing  pho,  then  say  to  -  gra 
and  cap  in  pronouncing  phy,  &.Q. 


with  the  height  and  latitudes,  increasing  from  the 
equator  to  the  poles  and  vice  versa.  The  oscillation  does 
not  vary  with  the  length  of  the  pendulum,  but  as  the 
square  root  of  the  length,  thi.s :  a  pendulum  oscillating 
in  one  second  should  be  four  times  shorter  to  give  an 
oscillation  of  one-half  of  one  second. 

To  oscillate  in  exactly  one  second  the  length  of  the 
pendulum  should  be  in — 


London,  .  . 

994  m 

m.  123,  Latitude  51°, 

31', 

08^/  N. 

Paris,    .  .  . 

993 

'  866, 

(( 

48 

50 

14  " 

New  York,  . 

993 

'  168, 

(( 

40 

42 

43 

Washing^ion, 

993 

009, 

(( 

38 

53 

23 

Kio  Janeiro, 

991 

'  693, 

22 

55 

13  S. 

(Pouillet's  Elements  de  Physique,  pp.  100,  et  seq.) 


PAET  II 


The  Development  m  the  Gelatine 
Peocess. 

Fixing,  Intensification,  and  Reduction. 


CHAPTEE  I. 


Generalities  on  the  Development. 


The  negative  cliches  on  dry  photo-films  are 
developed  by  the  alkaline  method,  that  is,  by 
exalting  or  assisting  the  reductive  property 
of  the  reagent,  pyrogallol,  etc.,  with  an  alkali. 

Experience  shows  that  when  the  developing 
solution  is  compounded  with  a  large  dose  of 
reagent  and  a  quantity  of  alkali  sufficient  to 
cause  the  reduction  of  the  silver  salt  modified 
by  the  agency  of  light,  a  greater  intensity  is 
obtained  in  the  high  lights  of  the  image,  which 
first  make  their  appearance,  the  half  tints 
hanging  back  for  a  period  so  much  the  longer 
as  the  exposure  is  shorter  ;  but  that  if  the 
dose  of  alkali  is  in  excess,  the  development 
proceeding  more  regularly  allows  the  little  im- 
pressed parts  of  the  film,  that  is,  those  corres- 
ponding to  the  half  lights  or  details,  to  develop 


70 


THE  PHOTOGRAPHIC  IMAGE. 


before  the  high,  lights  take  a  great  intensity. 
In  the  former  case,  harsh,  white  and  black 
images  are  produced  ;  in  the  latter  the  grada- 
tions from  light  to  shade  is  preserved. 

Hence,  the  development  should  be  regulated 
according  to  the  lighting  of  the  model  *  and 
the  exposure-time,  which  is  shown  by  the 
more  or  less  rapidity  of  the  development  and 
the  appearance  of  the  image  in  the  first  period 
of  the  same.  For  example  :  when  the  film  is 
over  exposed,  or  the  model  uniformly  lighted, 
the  image  having  a  great  tendency  to  flash  out 
in  all  its  parts  and,  therefore,  to  yield  an 
image  without  contrasts,  little  alkali  should 
be  added  to  the  developing  solution,  while 
in  the  opposite  case,  short  exposure-time  or 
lighting  with  great  oppositions,  it  is  neces- 
sary to  increase  the  dose  in  order  to  bring  out 
the  half  tints  in  time  or,  in  other  words,  before 
the  high  lights  have  gained  much  intensity. 

However,  the  development  should  never  be 
forced.  It  is,  on  the  contrary,  a  general  rule 
to  gradually  build  up  the  image,  whereby  the 
gradations  are  better  preserved  and  even  im- 


*  See  our  work  "  The  Lighting  in  Photographic 
Studios." 


GENERALITIES  ON  THE  DEVELOPMENT.  71 


proved.  Moreover,  a  great  excess  of  alkali 
may  produce  fogging  just  as  well  as  an  exag- 
gerated over  exposure  or  actinic  light  in  the 
dark  room.  It  also  may  cause,  for  the  reason 
before  explained,*  a  light  superficial  reduction 
of  the  silver  salt  not  acted  on  by  light  before 
the  details  are  fully  developed,  or  before  a 
suflicient  intensity  is  obtained. 

It  should  also  be  observed  that  the  results 
of  rapid  and  slow  development  are  not  exactly 
the  same.  By  the  former  method  exceedingly 
delicate  details  may  be  obliterated  owing  to 
the  coarseness  of  the  silver  molecules  ;  t  when, 
by  the  other  method,  they  will  be  well  defined 
and  quite  sharp  on  account  of  the  small  size  of 
these  molecules.  Therefore,  in  micro-photog- 
raphy, and  whenever  very  small  objects  are 
photographed,  it  is  advisable  to  develop  slowly 
— within  reasonable  limits,  of  course. 

From  what  precedes  we  can  already  deduct 
the  two   rules   following,  which  are  indeed 

*  See  the  action  of  the  alkalies  in  the  development. 

t  The  molecules  of  silver  bromide  formed  in  rapid 
emulsions  are  coarser  than  those  formed  in  emulsion  of 
ordinary  sensitiveness.  The  granulation  is  visible  on 
the  plates. 


72  THE  PHOTOGRAPHIC  IMAGE. 


exceedingly  important;  the  art  of  developing 
is  based  upon  them. 

1st.  In  cases  of  normal  and,  specially,  cf  short 
exposure-times y  or  when  the  model  is  lighted  hy 
strong  oppositions  of  lights  and  shades,  in  order  to 
secure  gradation,  the  details  should  he  first  brought 
out,  and  intensity  afterwards  obtained  by  increas- 
ing the  reductive  power  of  the  developer  with  large 
doses  of  the  reagent. 

In  operating  otherwise,  whatever  be  the 
photographic  process — wet  or  dry  collodion, 
gelatine  process — there  is  much  danger  of 
burying  the  half-lights  in  the  lights  or,  at 
least,  to  obtain  high  lights  without  penumbra. 

2nd.  When  the  plate  is  over  exposed,  or  the 
model  uniformly  lighted,  the  high  lights  should  be 
allowed  to  develop  before  the  delicate  details  com- 
mence to  appear,  always  pushing  to  intensity. 

Let  us  make  an  example  both  of  exposure- - 
time  according  to  the  lighdng,  and  of  develop- 
ment according  to  the  contrasts  dI  lights  and 
shades. 

"We  have  to  photograph  a  church  of  which 


GENERALITIES  ON  THE  DEVELOPMENT.  73 


the  front  is  brightly  illuminated  and  the  side 
in  the  shade.  Therefore  to  reproduce  the 
shadowed  side  we  lengthen  the  exposure-time 
more  than  it  is  necessary  to  photograph  the 
brilliantly-lighted  front,  otherwise  from  want 
of  exposure  it  would  be  impossible  to  develop 
the  former.* 

Now,  let  us  suppose  we  develop  the  latent 
image  with  what  is  termed  a  normal  developer, 
or,  in  other  words,  one  containing  a  full  dose 
of  pyrogallol ;  then  the  front  of  the  church 
will  appear  rapidly  and  acquire  a  great  opacity 
before  the  parts  in  the  shade  have  time  to 
develop  with  a  sufficient  intensity :  result,  a 
bad  negative. 

Hence,  the  exposure-time  is  not  by  itself 
sufficient  to  produce  a  good  picture.  If 
instead  of  operating  in  this  manner  we  modify 
the  reducing  action  by  compounding  the 
developer  with  a  small  dose  of  pyrogallol  and 
the  same  of  alkali  or,  even  better  in  the  case 
in  question,  by  increasing  the  proportion  of 
the  latter,  then  the  high  lights  or  parts  of  the 

*  We  have  selected  this  subject  as  being  a  difiBcult  one 
to  photograph.  We  could  as  well  have  taken  for  demon- 
stration a  model  lighted  a  la  Rembrandt,  so  called. 


74  THE  PHOTOGRAPHIC  IMAGE. 


cliurch  strongly  lighted  will  develop  first  as 
before,  but  slowly  gain  intensity  owing  to  the 
small  dose  of  pyrogallol,  while  the  details  or 
parts  in  the  shadow  will  more  rapidly  develop 
from  the  particular  action  of  the  alkalies  pre- 
disposing the  feebly-impressed  silver-bromide 
to  be  more  easily  acted  on  by  reducing-agents, 
and  gain  a  certain  intensity,  especially  by  not 
rocking,  for  reasons  which  are  explained  in  the 
following  lines :  result,  an  ensemble  very  satis- 
factory, if  not  perfect. 

Hence  the  rule  : 

Expose  for  the  details  in  the  shadows  and 
develope  to  force  them  out  and  produce  weak 
INTENSITIES :  the  high  lights  will  take  care  of  them- 
selves. 

Of  course  if  the  subject  is  wanting  in  con- 
trasts, the  exposure-time  should  be  short  and 
the  development  conducted  in  the  opposite 
manner. 

The  plates  are  developed  in  a  shallow  tray 
(glass  or  porcelain),  using  enough  solution  to 
cover  them.  The  porcelain  tray  of  the  writer 
is  provided  with  a  cardboard  lid  to  exclude 


GENERALITIES  ON  THE  DEVELOPMENT.  75 


the  light  when  the  development  slowly  pro- 
ceeds or  when  developing  orthochromatic 
plates  sensitive  to  red. 

When  the  developing  solution  is  energetic 
it  is  well  to  agitate  it  by  rocking  the  tray  from 
time  to  time,  else  marblings  will  very  likely  be 
formed  on  the  image. 

In  so  doing  the  development  is  more  rapid 
and  equal  on  every  part  of  the  film  which  is 
successively  washed  by  the  solution  at  the 
same  strength. 

By  diluting  the  developing  solution  and 
not  rocking,  one  obtains  better  half  tones, 
especially  in  cases  of  short  exposure-times, 
for^in  a  state  of  repose,  the  layer  of  liquid  in 
direct  contact  with  the  high  lights  of  the  image 
soon  exhausts  its  energy,  or  nearly  so,  the 
action  then  continuing  in  the  half  lights 
which  increase  in  vigor,  while  the  intensity 
remains  stationary,  so  to  say,  in  the  blacks  of 
the  cliche. 

The  image  need  not  be  developed  the  day 
the  plates  are  to  be  exposed.  It  may  be  post- 
poned for  a  week — a  month  without  injury. 
However,  in  a  certain  period  the  luminous 


76 


THE  PHOTOGRAPHIC  IMAGE. 


action  commences  to  vanish.  The  time  re- 
quired for  a  complete  evanescense  is  eighteen 
months,  according  to  some  experimenters,  three 
years  according  to  others ;  *  but,  whatever  it 
may  be,  it  is  a  fact  that  images  on  gelatine 
plates  developed  three  or  four  months  after 
exposure  require  a  more  energetic  treatment 
and  behave  as  if  the  exposure-time  was  short. 
Consequently,  in  a  journey  of  a  few  months  it 
is  advisable  to  somewhat  over  expose  if  the 
developement  should  be  done  at  home. 

To  ascertain  when  the  development  must 
be  stopped,  that  is,  when  the  general  intensity 
is  sufficient  to  yield  good  positives,  the  image 
should  be  viewed  by"  transparency ;  but,  the 
opacity  of  the  photo-film,  the  weak  light  by 
which  the  operations  should  be  done  render 
the  appreciation  rather  difficult.  It  is  true 
that  when  wet  the  gelatine  film  being  less 
sensitive  and  the  brown  color  to  it  imparted  by 
the  imbibition  of  the  developer  still  increasing 
its  insensitiveness  to  colored  light  permit  one 
to  examine  the  image  by  a  stronger  light  and 

*  The  evanescense  is  more  rapid  with  dry  collodion 
films. 


GENERALITIES  ON  THE  DEVELOPMENT.  11 


near  to  it;  but,  nevertheless,  the  difficulty 
exists. 

What  is  a  good  general  intensity  is  impossi- 
ble to  explain  otherwise  than  by  practical 
instructions.  However,  some  data  can  be 
given  to  guide  the  student. 

Generally  the  development  should  be  pushed 
until  the  details  in  the  whites  of  the  cliche  (the 
shadows  of  the  image)  are  quite  visible  by  trans- 
parency, and  the  whites  when  seen  by  reflection, 
veiled  so  that  the  most  delicate  details  are  not 
distinctly  visible,  the  blacks  being  apparent 
on  the  back  of  the  film.  When  the  film  is  of 
the  normal  thickness,  the  general  intensity  is 
then  very  likely  correct ;  but  if  the  film  is  thin 
the  development  should  be  pushed  until  the 
whole  image  is  visible  on  the  back ;  otherwise 
it  is  probable  that  the  intensity  will  net  be 
sufficient  after  fixing.  In  operating  in  this 
manner  it  may  happen  that  an  excess  of 
intensity  be  the  result ;  but,  as  it  will  be  seen 
further  on,  it  can  be  more  easily  corrected  than 
the  opposite  defect. 

The  reason  for  operating  as  said  above  is 
obvious  since  the  image  being  formed  by  the 
reduction  of  the  silver  haloid  starting  from  the 


78 


THE  PHOTOGRAPHIC  IMAGE 


surface  becomes  imbedded  in  the  film,  and  the 
intensity,  whish  is  a  consequence  of  the  more 
or  less  quantity  of  silver  reduced,  ceases  to 
gain  in  opacity  when  the  whole  thickness  of 
the  silver  haloid  is  converted  into  metal,  which 
is  seen  at  the  back  of  the  plate. 

On  the  whole  to  ascertain  whether  or  not 
the  image  is  well  developed  is  difficult.  It 
requires  a  great  experience ;  moreover,  the 
thickness  of  the  gelatine  film  much  varies  even 
in  plates  from  the  same  make,  the  develop- 
ment when  the  film  is  thick  requiring  to  be 
pushed  until  the  whole  image  disappears 
imbedded  in  a  veil  to  obtain  enough  intensity. 

As  a  rule — Develop  until  the  high  lights  and 
half  lights  are  visible  at  the  hack  of  the  filmy  and 
the  half  tints  somewhat  imbedded  in  the  deep 
shadows  when  viewing  the  image  by  reflection,'^ 

By  following  this  rule  a  sufficient  general 
intensity  will  be  obtained  without  much  alter- 

*  Many  amateur  photographers  do  not  print  from  their 
negatives.  They  will  never  know  what  is  a  real  good 
negative.  Indeed,  the  only  manner  to  acquire  experience 
in  judging  what  is  a  normal  intensity  is  to  make  the 
positive  proofs  oneself,  and  not  otherwise. 


GENERALITIES  ON  THE  DEVELOPMENT,  79 


ing  the  gradations  which  must  be  preserved 
between  the  local  intensities. 

These,  termed  local  and  general  intensitlea, 
must  be  explained. 

The  negative  image  is  formed  by  various 
opacities  of  reduced  silver  which,  being  the 
greatest  in  the  pure  whites,  diminish  in  intens- 
ity in  the  half  lights,  etc.,  while  the  great 
shadows  or  pure  blacks  are  represented  by  the 
bare  or  slightly  veiled  glass.  Necessarily 
these  various  intensities  must  keep  a  certain 
relation  between  themselves  to  yield  a  positive 
image  with  the  gradations  of  lights  and  shades 
of  the  model.  These  are  termed  local  intens- 
ities. They  should  be  very  intense  in  the  high 
lights,  less  so  in  the  half  lights,  etc. 

Here  we  must  open  a  parenthesis — 

To  obtain  positive  impressions  from  negative 
cliches  a  sheet  of  paper  is  floated  on  a  solution 
of  ammonium  and  barium  chlorides  com- 
pounded with  or  without  an  organic  substance 
— allumen  is  generally  employed.  When  dry, 
this  paper  is  laid  for  about  two  minutes  on  a 
bath  of  silver  nitrate,  whereby  the  chlorides 
are  converted  into  silver  chloride,  which  .ight 


80  THE  PHOTCaRAPHlO  IMA  GE. 


blackens  and  reduces  by  elimination  of 
chlorine.  Hence,  for  the  purpose  in  question 
the  silvered  and  dry  paper  is  laid  on  a  negative 
cliche  in  a  printing  frame  and  the  whole  ex- 
posed to  the  sunlight's  action. 

During  the  period  of  insolation  the  light 
passing  through  the  various  intensities  of  the 
silver  deposit  forming  the  negative  image, 
reduces  the  silver  chloride  more  or  less  rapidly 
and,  therefore,  in  greater  or  less  quantities 
according  as  it  finds  a  more  or  less  free 
passage  to  the  silver  chloride.  Now,  if  the 
general  intensity  is  deficient,  that  is,  if  the 
negative  image  is  too  transparent  in  all  its 
parts,  it  is  evident  that  the  positive  will  be 
grey,  without  sufficient  contrasts,  since  the 
light  will  find  an  easy  ingress  through  all  the 
various  thicknesses  of  the  silver  deposit  of  the 
negative  which  are,  so  to  say,  nearly  of  equal 
opacity. 

On  the  other  hand,  should  the  reduction  in 
high  lights  be  strong  and  cover  the  half  lights, 
these  parts,  letting  only  a  small  amount  of 
light  to  pass  through,  will  cause  the  corres- 
ponding parts  of  the  silver  chloride  to  be 
slowly  reduced,  while  the  light  easily  passing 


GENERALITIES  ON  THE  DEVELOPMENT,  81 


through  the  transparent  parts  (the  details  or 
half  shadows)  and  freely  through  the  bare 
parts  of  the  glass  (the  deep  shadows)  will 
blacken  the  corresponding  parts  of  the  silver 
paper  long  before  the  others  being  sufficiently 
pri7ited. 

The  result  need  not  be  told — it  is  obvious. 
This  being  borne  in  mind  by  the  reader  we 
proceed. 

During  the  development  the  high  lights 
first  make  their  appearance,  then  the  half 
lights,  and  so  forth.  Now,  when  the  delicate 
tints  are  well  out,  the  development  proper  is 
at  an  end ;  but  the  lights — if  the  operation  has 
been  well  conducted — are  not  sufficiently  in- 
tense and  a  fortiori  the  half  tints.  Therefore, 
if  the  development  were  then  stopped  the 
general  intensity  would  be  weak  and  the  nega- 
tive cliche  would  never  yield  but  a  flat,  weak 
positive  image.  Hence,  one  must  necessarily 
let  the  development  go  on  to  obtain  a  dense 
enough  general  intensity,  and  as  the  reductive 
action  is  always  greater  in  the  parts  most 
impressed,  the  gradation  of  the  local  intens- 
ities will  be  preserved. 

However,  if  the  development  is  pushed  to 


82 


THE  PHO  TO  GRA  PHIC  IMA  GE. 


excess  the  contrasts  will  increase  and  as  tlie 
half  lights  would  generally  be  buried  in  the 
lights,  the  cliche  will  print  an  image  without 
details  in  the  lights.  This  defect  often  ob- 
served in  instantaneous  photographs,  so-called, 
arise  from  the  development  being  pushed  so 
as  to  obtain  all  the  details  in  the  deep 
shadows,  while  the  exposure  being  short  they 
should  be  sacrificed. 

In  the  next  pages  we  will  explain  the  modus 
operandi  of  the  development  with  pyrogallol^ 
which,  of  course,  apply  to  the  other  reagents 
— for  the  different  circumstances  which  may 
present  themselves.    It  is  based  on  this  rule  : 

The  development  should  he  conducted  according 
to  the  manner  the  image  commences  to  appear  and 
its  character^  either  by  increasing  the  reductive 
power  of  the  developing  solution  to  obtain  intensity 
and  contrasts,  or  by  subduing  or  modifying  its 
mode  of  action  to  obtain  softness  and  harmony. 

This  rule  obviously  necessitates  that  the  de- 
velopment  should  be  slow  at  the  beginning  at 
least,  in  order  to  allow  the  operator  to  follow 
its  various  phases  and  make  the  modifications 
in  time. 


CHAPTER  II. 


The  Development  with  Pyeogallol. 


Here  is  a  gelatine  bromide  of  silver  plate 
of  the  ordinary  sensitiveness.  It  has  been 
exposed.  Lens  :  a  Dallmeyer  rapid  rectilinear 
11  inches  equivalent  focus ;  diaphragm,  ^. 
Subject :  a  view  in  Staten  Island,  New  York. 
Exposure-time :  3  seconds ;  it  is  a  normal 
exposure  as  far  as  one  can  judge  a  priori. 

We  first  prepare  the  following  solutions  to 
compound  the  developer : 

A.   Sodium  sulphite    ...    60  parts. 
Pyrogallol      .     .     .     .    15  «* 
Nitric  acid      ....     4  " 
Water,  to  make    .     .     .480  « 

This  solution  keeps  well.  However,  we 
advise  one  not  to  prepare  it  in  greater  quan- 
tity than  it  is  wanted  for  use  in — say  a  week. 


84 


THE  PHOTOGRAPHIC  IMAGE. 


B.    Potassium  carbonate 


Sodium  carbonate  cryst.* 
Sodium  sulpliite 
"Water,  to  make 


20  parts. 
40  " 


40 


480 


C.    Potassium  bromide 
Water 


1  part, 
10  parts. 


These  two  solutions  keep  well.  C  is  the 
restrainer. 

To  develop,  equal  volumes  of  A  and  B 
diluted  with  three  volumes  of  water  would 
be  right  were  the  exposure-time  exact  and 
every  thing  else  equal — the  intensity  of  the 
light,  the  color  and  lighting  of  the  subject, 
etc. ;  but  this  we  do  not  know  with  certainty, 
and  we  have  to — and,  indeed,  we  always  have 
to  feel  our  way,  moreover,  by  treating  the 
plate  with  the  solution  so  compounded  the 
half  tints  in  the  high  lights  would  likely  be 
blocked  up  before  the  delicate  details  in  the 
shadows  are  developed.  Therefore,  we  add 
only  half  a  volume  of  pyrogallol,  immerse  the 
plate  in  the  solution  and,  from  time  to  time 
rocking  the  tray  we  let  the  action  proceed 
until  the  details  in  the  shadows  are  well 

*  Not  the  washing  soda  which  is  exceedingly  impure 
and  tends  to  produce  a  peculiar  yellow  fog. 


THE  DEVELOPMENT  WITH  FYROGALLOL.  85 


defined  when,  by  adding  the  remainder,  the 
general  intensity  will  be  soon  obtained.  By 
this  manner  of  operating  we  let  the  half  tints 
develop  before  pushing  to  intensity  with  large 
doses  of  pyrogallol. 

Now,  the  plate  may  be  a  little  over  exposed, 
which  we  will  see  by  the  half  tints  making 
their  appearance  soon  after  the  high  lights. 
In  this  case  we  at  once  add  a  few  drops  of  G 
to  check  the  development,  adding  at  the  same 
time  one  volume  of  A. 

Presently,  let  us  suppose  that  the  exposure- 
time  is  very  short,  as  it  is  most  generally  the 
case  when  exposing  by  the  shutter ;  we  must 
then  not  only  allow  or  force  the  details  to 
develop  but  prevent  the  high  lights  from 
gaining  intensity. 

To  that  end  some  authors  advise  to  develop 
rapidly  by  treating  the  plate  with  an  energetic 
solution  to  develop  the  whole  image  at  once 
— before  the  high  lights  have  time  to  intensify. 
We  found  that  the  manner  of  operating  with 
pyrogallol  was  far  from  always  being  effective  ; 
moreover,  rapid  plates  so  treated  are  liable 
to  be  fogged  and  the  development  is  not 
under   absolute   control,    which    latter  we 


86 


THE  PHOTOORAPBIC  IMAGE. 


think  quite  objectionable.  We  do  not  like  to 
work  blindfolded.  Hence,  we  prefer  a  slow 
development  with  a  dose  of  "patience." 
It  is  a  fact  observed  by  every  operator  that,  by 
diluting  the  developer  and  rocking  in  the  first 
period  of  the  development,  then  letting  the 
action  proceed  without  further  agitating  the 
liquid,  better  half  tones  are  obtained. 

We  operate  in  this  manner :  we  take  one 
volume  of  By  dilute  it  with  five  volumes  of 
water,  immerse  the  plate  in  the  solution,  let 
it  soak  for  a  minute,  then  add  half  of  one 
volume  of  A  and  let  the  action  proceed ;  then, 
according  as  the  image  appears  we  add  more 
pyrogallol  with  or  without  alkali,  or  allow  the 
image  to  develope  without  any  doctoring,  or 
still  reduce  the  energy  of  the  developer  by 
dilution — but  this  happens  only  in  cases  of 
very  short  exposure-times  bordering  to  a  real 
under  exposure. 

If  the  plate  has  been  over  exposed  we 
operate  in  the  opposite  manner.  We  mix  one 
volume  of  A  with  three  volumes  of  water, 
let  the  plate  soak  in  this  for  a  moment  and 
then  add  half  a  volume  of  B, 


THE  DEVELOPMENT  WITH  PYROGALLOL.  87 


Now,  it  may  happen,  notwithstanding  the 
the  excess  of  exposure,  that  certain  details 
hang  back  or,  which  is  more  likely,  that  all 
the  details  appear  simultaneously  soon  after 
the  high  lights.  In  the  former  case,  if  they  do 
not  make  their  appearance  within  thirty 
seconds  after  the  lights,  it  is  evident  that  more 
alkali  should  be  gradually  added,  waiting  after 
each  addition  to  ascertain  what  is  the  effect 
produced.  In  the  other  case,  if  all  the  parts 
of  the  image  appear  almost  at  once  and,  there- 
fore, without  sufficient  gradations,  the  develop- 
ment should  be  restrained  by  the  addition 
of  potassium  bromide. 

The  development  needs  no  doctoring  where 
the  image  comes  out  gradually  :.  the  high 
lights  first ;  then,  one  after  the  other,  the  half 
lights  and  the  details  in  the  shadows. 

The  rule  for  over  exposure-time  is  ; 

To  cause  the  high  lights  to  gain  some  intensity 
before  forcing  out  the  details,  unless  the  opposition 
he  strong. 

Here  is  a  plate.  We  do  not  know  how  it 
ha^  been  exposed,  what  is  the  subject,  etc. 


88  THE  PHOTOGRAPHIC  IMAGE. 


No  memorandum  has  been  taken.  How  shall 
we  proceed? 

We  compound  the  developer  with  equal 
volumes  of  A  and  B,  and  dilute  with  five 
volumes  of  water. 

The  image  comes  out  regularly  in  gradua- 
tions.   We  let  the  action  go  on. 

The  details  in  the  shodows  appear  soon 
after  the  lights — over  exposure ;  we  restrain 
with  potassium  bromide  and  add  another  dose 
of  pyrogallol. 

The  details  long  hang  back — short  exposure ; 
we  add  more  alkali  and,  when  the  details  are 
well  defined,  we  increase  the  dose  of  pyrogallol 
if  it  is  necessary  to  obtain  more  intensity. 

This  manner  of  operating  is  termed  tentative 
development. 

As  is  seen  by  these  examples  the  method 
consists  to  add  the  pyrogallol  or  the  alkali  by 
small  doses  in  order  that — the  image  develop- 
ing slowly  and  gradually  according  to  the 
contrasts — we  can  at  any  time  during  the 
operation  have  control  of  the  development 
and,  therefore,  produce  any  effect  we  judge 


THE  DEVELOPMENT  Wl TH PYROGALLOL.  89 


best  to  make  an  image  not  only  photographic- 
ally good  but  also  having  an  artistic  value. 

In  the  above  instructions  we  have  considered 
the  development  mostly  in  relation  to  the 
exposure-time.  If  we  consider  it  according  to 
the  lighting  or  the  oppositions  the  treatment 
is  similar."^  When  the  lighting  of  the  subject 
is  uniform,  the  development  is  made  as  in 
the  cases  of  over  exposures,  that  is,  with  a 
restrained  developer. 

We  shall  give  another  and  last  example  of 
the  development  of  subjects  having  strong 
contrasts  of  whites  and  blacks,  which  are  of  so 
frequent  occurrence  both  in  portraiture  and  in 
out  door  photography. 

Here  is  a  landscape  :  a  Queen  Anne  cottage 
and  trees  in  the  foreground,  a  road  bordering 
a  river,  mountains  in  the  distance.  This 
is  a  common  subject,  but  quite  difficult  to 
photograph  well — that  is,  to  develop  —  on 
account  of  the  contrast  of  the  white  cottage 
with  the  dark-green  foliage ;  the  road  should 
not  be  snowy,  the  distant  mountains  in  the 

*  On  this  subject  see  our  work,  *'  The  Lighting  of 
Photographic  Studios.'* 


90 


THE  PHOTOGRAPHIC  IMAGE, 


slightly  misty  atmosphere  of  autumn  not 
buried  in  the  sky,  etc. 

We  have  over  exposed  on  account  of  the 
trees  and  other  dark  objects  which  are  there. 
To  develop  we  immerse  the  plate  into  a  solu- 
tion of  one  and  one-half  volumes  of  B  diluted 
with  three  volumes  of  water  and,  if  the  plate 
is  a  very  rapid  one,  we  add  a  few  drops  (not 
many)  of  C  to  prevent  fogging.  In  this  we 
let  the  plate  soak  for  a  minute  ;  then,  pour- 
ing off  the  solution,  we  add  one-eighth  of  one 
volume  of  A  and  pour  back  the  mixture  in 
the  tray  over  the  plate.  Now,  the  white  house 
will  gradually  appear,  but  without  gaining 
much  in  intensity,  then  the  water,  then  the 
road  will  come  out,  then  the  mountains  and, 
lastly,  after  a  certain  period,  say  three  minutes, 
the  foliage  will  be  visible,  the  intensity 
meanwhile  gaining  little  in  the  parts  which 
first  made  their  appearance. 

When  the  details  in  the  foliage  are  fairly 
out,  one-quarter  of  one  volume  of  A  is  added 
and  the  whole  picture  allowed  to  slowly 
intensify,  and  when  every  thing  is  well  defined 
and  apparent  by  viewing  the  picture  by  trans- 
parency, if  the  general  intensity  is  not  opaque 


THE  Development  with  pyroga llol.  9i 


enough,  one  adds  a  full  dose  of  A  with  some 
drops  of  C  and  in  a  short  time  the  cliche 
will  acquire  good  printing  qualities. 

The  development  of  such  a  subject  is  neces- 
sarily slow.  It  takes  from  15  to  18  minutes, 
and  even  a  longer  period  if,  for  instance,  it  is  a 
snow  or  a  waterfall  scenery  with  figures,  trees, 
rocks,  etc.,  as  the  dose  of  pyrogallol  should  be 
still  smaller  than  that  above  advised  to  start 
the  development,  in  order  to  restrain  the 
intensification  and  thus  effectively  preserve 
the  modelling  of  the  whites  while  the  details 
in  the  dark  objects  are  hanging  back.  In 
operating  otherwise,  that  is,  by  using  an  ener- 
getic developer,  either  the  half  tints  in  the 
whites  should  be  satisfied  to  develop  the 
objects  in  the  dark  or  the  latter  will  be  a  black 
mass  without  details  if  the  development  is 
stopped  to  preserve  the  former. 

Orthochromatic  plates  should  also  be  treated 
with  a  small  proportion  of  pyrogallol  to  begin 
the  development.    The  reason  is  obvious. 

Local  development  is  done  by  raising  the 
temperature  of  those   parts   which  require 


02 


THE  PHOTOGRAPHIC  IMAGE. 


to  be  forced  out  or  intensified.  The  manner  of 
doing  this  is  simple  enough;  it  suffices  to 
breathe  on  the  parts  in  question  through  a 
small  glass  tube  during  the  development,  using 
not  too  energetic  a  solution. 

Mr.  H.  Fourtier  operates  in  the  opposite 
manner  for  the  same  purpose.  He  restrains 
the  development  in  the  parts  with  intensity 
too  rapidly  by  touching  them  with  a  brush 
dipped  in  the  following  solution  after  washing 
the  plate  and  draining,  and  this  done  proceeds 
as  usual : 

Potassium  bromide  .      .     4  parts. 
Potassium  citrate    .      .     2  *' 
Water  100  " 

The  above  constitutes  a  strong  restrainer. 

The  following  is  a  developer  for  line-works : 

A^.   Sodium  sulphite  cryst.    .  40  parts. 
Citric  acid     ,     .     .     .      2  " 
Pyrogallol     ....       8  " 

Water   480  ** 


jB2.   Sodium  carbonate 
Potassium  bromide 
Water 

Equal  volumes. 


40  parts. 

2  " 
480  " 


THE  DEVELOPMENT  WITH  PYROGALLOL.  93 


We  "will  now  give  a  summary  of  the  rules 
and  afterwards  describe  the  processes  em- 
ployed to  fix,  intensify  or  reduce  the  opacity 
of  cliches,  and  then  explain  the  development 
with  the  other  reducing  agents. 


CHAPTER  III. 


SUMMAEY     OF     THE     RuLES  ReGULATIKG 

THE  Exposure  and  its  Development. 


I.    Give  full  exposure. 

IL  Over  expose  so  much  the  more  as  the 
model  shows  greater  contrasts.* 

III.  Under  expose  but  little,  if  any,  when 
the  model  is  uniform.  Vigor  is  easily  obtained 
by  the  development. 

*  Whenever  the  subject  is  lighted  by  violent  contrasts 

one  should  not  hesitate  of  exposing  3,  4  times 

longer  than  the  so-called  normal  exposure  requires  for 
one  may  over  expose  without  exposing  enough,  that  is, 
without  reaching  that  moment  of  the  reversal,  ob.^erved 
by  Janssen,  when  the  lights  are  re-impressed.  But  then 
one  should  commence  to  develop  with  a  developer  so 
much  the  weaker  as  the  exposure  has  been  more 
lengthened. 


SUMMARY  OF  THE  RULES. 


95 


ly.  Always  eommence  slowly  tlie  develop- 
ment. It  is  most  important  to  have  it  under 
control  at  the  very  first  period  of  the  operation 
in  order  to  be  able  of  modifying  in  time  its 
action,  as  judged  necessary  by  the  manner  the 
image  makes  its  appearance. 

V.  With  a  given  quantity  of  pyrogallol  the 
rapidity  and  intensity  of  the  reduction  increase 
with  the  proportion  of  alkali,  but  beyond 
which,  the  excess  of  alkali  causes  the  half 
tints  to  develop  more  rapidly  than  before. 

VI.  Increasing  the  dose  of  alkali  corre- 
sponds to  diminishing  that  of  pyrogallol  and 
vice  versa. 

VII.  The  details  appear  more  rapidly  while 
the  high  lights  (blacks)  slowly  intensify  when 
the  developing  solution  contains  a  small 
quantity  of  pyrogallol  with  an  excess  of 
alkali. 

VIIL  By  increasing  the  dose  of  pyrogallol 
the  developer  is  more  energetic,  and  the 
blacks  rapidly  intensify  in  proportion  to  their 
value. 


96 


i'HE  PHOTOGRAPHIC  IMAGE. 


IX.  By  diminishing  the  dose  of  alkali  the 
result  is  the  same,  but  the  development  pro- 
ceeds more  slowly. 

X.  When  the  exposure-time  is  normal  and 
the  subject  well  lighted,  the  plate  should  be 
treated  to  obtain  the  details  and  then  intensi- 
fied, which  is  easily  done  in  this  case  by  adding 
the  pyrogallol  in  small  doses  at  a  time. 

XI.  When  the  exposure  time  is  short,  or 
what  is  the  same  thing  as  to  the  result,  when 
the  model  is  lighted  by  strong  oppositions  of 
lights  and  shades,  the  developing  solution 
should  be  compounded  with  a  small  dose  of 
pyrogallol  and  a  full  dose  of  alkali,  then 
diluted,  whereby  the  half  tints  appear  grad- 
ually while  the  black  slowly  intensify.  Usually 
there  is  no  necessity  of  doctoring  the  developer; 
it  suffices  to  let  the  action  go  on.  The  develop- 
ment is  slow. 

Some  authors  advise  to  develop  with  a  con- 
centrated solution  compounded  with  a  large 
dose  of  alkali  in  order  to  develop  the  image  at 
once  in  all  its  parts,  so  to  say ;  then  pushing 
to  intensity  by  restraining  the  action  with 


SUMMARY  OP  THE  RVLm. 


97 


potassium  bromide.  The  following  is  a 
formula  for  drop  shutter  exposures : 

Pyrogallol  .     .     .  .     5.  parts.* 

Potassium  carbonate  .    25.  ** 

Potassium  bromide  .     0.25  part. 

Sodium  sulphite     .  .30.  parts. 
Water     .     .     ;     .     480.  « 

We  recommend  the  former  method. 

XII.  In  cases  of  over  exposure-time,  or 
when  the  model  is  lighted  too  uniformly,  the 
developing  solution  should  be  compounded 
with  a  full  dose  of  pyrogallol  and  its  action 
somewhat  restrained  in  order  to  push  to 
intensity  at  once,  or  when  the  details  are 
faintly  visible. 

XIII.  The  use  of  the  restrainer,  potassium 
bromide,  is  regulated  according  as  the  image 
appears  too  uniformly.    No  rule  can  be  given. 

*  Pyrogallol  should  be  added  by  degrees,  else  too 
much  intensity  may  be  obtained  at  first.  This  is  the 
only  safe  method.  It  can  happen  that  by  operating 
otherwise  good  pictures  can  be  obtained  ;  but,  then,  the 
exposure  is  very  likely  sufficient,  notwithstanding  the 
plate  having  been  exposed  by  the  drop  shutter,  if  the 
subject  is  lighted  without  great  oppositions,  the  dia- 
phragm large,  the  plate  very  rapid,  &c. 


98 


THE  PHOTOGRAPHIC  IMAGE. 


The  point  to  bear  in  mind  is  that  a  restrainer 
acts  in  opposition  to  the  alkalies,  tending  to 
produce  contrasts  by  retarding  the  develop- 
ment of  the  half  tints  much  more  in  proportion 
than  that  of  the  lights,  which  latter,  in  reason 
of  being  strongly  impressed  are  always  acted 
on  with  sufficient  energy  by  the  reagent. 

When  the  exposure-time  is  in  excess,  and 
when  developing  with  a  large  dose  of  alkalies, 
it  is  quite  advisable  to  add  the  restrainer  in 
small  quantities  to  the  developer  in  order  to 
prevent  fogging  and  therefore,  to  obtain  clear 
negative  cliches.* 

XIV.  Develop  to  first  obtain  gradations, 
and  then  the  general  intensity. 

XY.  In  case  of  instantaneous  (short)  ex- 
posures, one  should  conduct  the  development 
to  obtain  the  best  possible  picture  of  the 
svhjed  without  regard  to  the  secondary  parts 
which,  often,  should  be  sacrificed;  for,  by 
trying,  for  example,  to  obtain  all  the  details  in 
the  deep  shadows,  the  half  lights  may  be 
buried  in  the  high  lights  and  nothing  but  a 

*  See  the  generalities  on  the  Enstrainers. 


SUMMARY  OF  THE  RULES,  99 


harsh,  white  and  black  image  will  be  the 
result. 

XYI.  When  photographing  white  and  black 
subjects  (copies  of  engravings,  etc.)  the  ex- 
posure-time should  be  short  in  order  to  avoid 
solarization  ;  or,  in  other  words,  to  obtain  pure 
whites.* 

In  this  case  the  developer  should  be  strong 
and  restrained.  An  old  hyroquinone  developer 
gives  good  results,  the  objection  is  its  liability 
of  producing  yellow  fog. 

XYII.  A  diluted  developing  solution  acts 
as  a  concentrated  one,  provided  the  relative 
proportions  of  the  components  are  the  same. 
The  only  difference  is  that  the  former  acts 
more  slowly. 


*  See  Introduction. 


CHAPTER  IV. 


Fixing. 


When  the  image  is  developed  and  sufficiently 
intense,  it  should  be  thoroughly  washed  and 
fixed.  This  operation  has  for  its  object  to 
eliminate  from  the  film  the  unaltered  silver 
salts,  as  they  would  blacken  under  the  action 
of  light  and  spoil  the  cliche. 

According  to  Mr.  A.  Duttens  the  film  can  be 
rendered  insensitive  to  light  so  as  to  allow  one 
to  fix  the  image  at  any  time  when  convenient. 
It  suffices  to  wash  well  the  plate  after  develop- 
ment ;  then,  to  immerse  it  for  five  minutes  in  a 
solution  of  5  parts  each  of  potassium  bromide, 
acetic  acid,  and  alum,  dissolved  in  150  parts  of 
water.  On  its  removal  from  the  solution  the 
plate  is  well  rinsed,  then  dried ;  or,  before  this, 


FIXING. 


101 


flowed  several  times  with  methylated  alcohol 
to  hasten  the  desiccation. 

Before  fixing  it  is  advisable  to  clear  the 
cliche  from  any  yellow  fog,  and  to  wash  out  or 
decompose  the  oxidized  developer  and  the 
alkali  in  order  to  prevent  the  formation  of  a 
peculiar  fog— greenish  by  reflection,  light  red 
by  transparency — consisting,  according  to  some 
authors,  of  a  very  thin  layer  of  silver  formed 
by  the  reduction  of  the  thiosulphate  of  silver 
and  sodium,  occuring,  especially,  when  the 
fixing  is  done  in  the  light.  According  to  Dn 
H.  W.  Yogel,  but  not  very  likely,  it  is  due  to 
traces  of  silver  bromide  retained  in  the  film. 
This,  or  a  pink  general  coloration  can  be  pro- 
duced at  will  by  fixiDg  in  an  old  weak  solution 
of  thiosulphate  bath  held  in  a  tin  tray. 

The  clearing  solution  consists  of 
Hydrochloric  acid,  or 

Aqua  regia  (6  HCH- HNO3)     .     .     2  parts.* 
Water  48  ** 


•  The  aqua  regia  should  be  prepared  a  few  hours 
before  use.  It  can  be  kept  in  stock  in  a  glass-stoppered 
vial. 


102  THE  PHOTOGRAPHIC  IMAGE. 


The  cliche  should  remain  for  two  or  three 
minutes  in  the  solution,  then  carefully  rinsed 
before  fixing. 

Common  alum  has  no  action  as  a  clearing 
agent  either  before  or  after  fixing  and  is,  we 
think,  objectionable.  If  employed  before  fix- 
ing, the  alkali  retained  in  the  film  decomposes 
it  with  precipitation  of  aluminia  in  the  film  or 
adhering  on  its  surface,  forming  yellowish- 
white  stains — opaque  by  transparency  : 

Al2(S04)3K2S04  +  3  K^COa^  4  K^SO,  +  A12034 
3  CO2 

With  sodium  thiosulphate,  aluminium  and 
sulphur  are  thrown  down  : 

3  Na2S203  + Al2(S04)3     3  Na^SO.+AlA+Ss-f 
3  SO2. 

In  these  actions  alum  (double  sulphate  of 
aluminium  and  potassium)  acts  through  the 
aluminium  salt. 

The  latter  equation  shows  how  useless  it  is 
to  add  alum  to  the  fixing  bath,  since  being 
decomposed  it  has  no  action  on  gelatine,  but 
liberates  sulphur  dioxide,  SO2,  and  causes 


103 


the  sulpliuration  of  the  silver  forming  the 
image. 

The  cliche  is  fixed  by  immersion  in  a  solu- 
tion of  sodium  thiosulphate  (hyposulphite), 
the  concentration  of  which  need  not  exceed  20 
per  cent  of  water.  In  dissolving,  the  thiosul- 
phate produces  considerable  cold,  which  might 
be  utilized  in  the  warm  season  lo  cool  water ; 
but  the  bath  should  be  employed  at  common 
temperatures— 15°  C.  to  20°  C. 

In  the  fixing  bath  the  unaltered  silver  salt  is 
dissolved  with  formation  r^f  9  double  thiosul- 
phate of  silver  and  sodium  • 

AgBr+Na2S203=NaAgS203+NaBr. 

Another  double  salt  containing  two  equiv- 
alents of  sodium  thiosulphate  is  formed  when 
the  fixing  bath  is  very  weak  or  its  action 
almost  exhausted.^  It  is  insoluble,  turns 
brown  and  then  black  in  the  light,  and  even  in 
darkness.t    It  is  also  formed  when  the  cliches 

*  A  fixing  batii  containing  100  grams  of  sodium  thio- 
sulpliate  (hyposulphite)  should  not  be  used  to  fix  more 
than  15  gelatine  plates  15x21  centimetres. 

f  Silver  thiosulphate  is  rapidly  decomposed  by  day 
light,  the  changes  occuring  even  r.c  soon  as  it  is  formed. 
It  is,  therefore,  advisable  to  fix  by  a  very  diffused  or 
artificial  light. 


104  THE  PHOTOGRAPHIC  IMAGE. 


— or  the  photograplis  on  paper — are  removed 
aud  washed  before  all  the  silver  haloid  is 
entirely  dissolved : 

2  AgBr+3  Na2S203=:Na,Ag2(S203)3+2  NaBr. 

When  the  silver  salt  is  dissolved,  which  is 
easily  ascertained  by  examining  the  back  cC 
the  plate,  it  is  well  to  let  the  plate  remain  a 
little  while  longer  in  the  fixing  solution ;  or, 
as  recommended  for  fixing  photographs  on 
paper,  to  place  it  for  a  few  minutes  in  new 
solution  at  about  10  parts  of  tliiosulphate  for 
100  parts  of  water,  in  order  to  insure  a  perfect 
fixation. 

When  fixed,  the  film  must  be  thoroughly 
washed  to  free  it  from  sodium  thiosulphate 
and  consequently  from  the  double  thiosul- 
phate, and  as  traces  of  these  salts,  being 
mechanically  retained  in  the  gelatine  film,  can 
not  b3  eliminated  by  washing  alone,  one 
should  have  recourse  to  a  chemical  action  to 
decompose  them. 

This  is  necessary  for  the  following  reasons  : 
Sodium  thiosulphate  in  presence  of  damp- 
ness and  the  air  is  transformed  into  sodium 


FIXING, 


105 


sulphate  with  formation  o£  snlphureted  hydro- 
gen : 

Na^S^Os+H^O^Na^SO^+H^S. 

If  oxygen  does  not  intervene,  sodium  sul- 
phite is  formed  and  sulphur  liberated  : 

Na2S203=Na2S03+S. 

All  the  acids,  even  very  diluted  (acid  fumes 
in  the  air,  for  example),  decompose  it,  evolving 
thiosulphuric  acid  which  is  resolved  into  sul- 
phurous acid  and  sulphur  as  it  forms,  thus : 

Na2S203+2  H0i=H2S2O3+2  NaCl, 
and  H,S203=S02+H20+S. 

 y 

On  ihe  other  hand,  silver  sodium  thiosul- 
phate  splits  into  silver  sulphide  and  sulphuric 
acid,  which  latter  acts  on  the  sodic  salt  as  said 
above : 

Ag2S203+H20=Ag2S+H2SO,. 

Now  all  these  actions  necessarily  convert 
the  metallic  silver  forming  the  photographic 
image  into  sulphide  which,  in  time,  in  presence 
of  organic  matters,  dampness,  and  other  in- 
fluences, undergoes  certain  isomeric  changes 
producing  the  phenomenon  known  in  photog- 
raphy under  the  name  of  fading. 


106  THE  PHOTOGRAPHIC  IMA  GEl. 


The  most  expeditious  manner  of  washing  is 
to  place  the  plates  in  the  grooves  of  a  jmall 
wooden  tank  into  which  the  water  constantly 
renewed  enters  from  the  bottom  and  runs  off 
from  above.  In  such  an  apparatus  the  plates 
are  washed  in  one  or  two  hours. 

The  complete  elimination  of  sodium  thiosul- 
phate — but  that  mechanically  retained  in  the 
film — is  ascertained  by  collecting  the  drippings 
from  the  plate  in  a  small  quantity  of  a  very 
diluted  solution  of  silver  nitrate  or  an  aqueous 
solution  of  iodine  prepared  by  shaking,  a  drop 
of  tincture  of  iodine  in  water.  If  any  of  the 
salt  in  question  is  present  the  latter  solution 
is  decolored ;  in  the  former  a  brown  precipitate 
rapidly  turning  black  is  formed. 

To  eliminate  the  last  traces  of  thiosulphate 
it  suffices  to  immerse  the  plate  for  a  moment 
in  a  solution  of  Eau  de  Javelh^  at  1  per  120  of 

*  Eau.  de  Javelle  is  prepared  by  dissolving  1  part 
of  chloride  of  lime  (bleaching  powder)  in  14  parts  of 
water,  filtering,  then  adding  a  warm  solution  of  1.2  parts 
of  potassium  carbonate  in  6  parts  of  water. 

This  compound  is  a  mixture  of  hypochlorite  and 
chloride  of  potassium.  It  acta  in  chemical  actions 
through  chlorine  which  decomposes  water  in  setting 
oxygen  free. 


107 


water,  and  then  rinse  the  film  well  under  the 
tap. 

This  process  is  due  to  Maxwell  who  recom- 
mended it  in  1853  for  a  similar  purpose  in  the 
printing-out  silver-process. 

The  chemical  action  consists  in  converting 
the  thiosulphate  into  sodium  sulphate  which 
is  harmless  and,  being  very  soluble,  can  be 
washed  off  easily : 

Na2S203+4:  KC10+H20=2  NaHS0,+4  KCl. 

The  following  fixing  solution  if  employed 

by  many  operators  on  the  recommendations  of 

Herbert  B.  Bevkely  (1883) : 

Sodium  thiosulphate  (hyposulphite)    .  95  parts. 
Sodium    bisulphite,  commercial, 

solution  at  30°  Baume       .      .       .  20  " 

Water   480  " 

The  advantage  claimed  is  that  the  solution 
does  not  become  muddy  by  use,  clears  the 
cliches  and  produces  a  slight  intensification 
due  to  a  more  or  less  complete  sulphuration  of 
the  silver.  The  objection  is  that  any  reduc- 
tion of  intensity  is  more  difficultly  effected.  It 
is,  however,  a  good  process,  preventing  yellow 
fog  either  from  pyrogallol,  hydroquinone  or 
eikonogen  to  occur  in  the  fixing  bath. 


CHAPTER  V 


Intensification. 


Weak  negatives  can  be  intensified  in  many 
ways.  The  process  based  on  the  chemical 
changes  taking  place  when  mercurous  chloride 
(calomel)  is  treated  by  ammonia  or  sodium 
thlosulphate  (hyposulphite^  is  the  most  em- 
ployed. 

It  was  devised  by  Scout  Archer  who,  if  he 
was  not  the  first  to  use  collodion  as  a  medium 
to  Iiold  the  silver  haloids,  has  nevertheless  the 
very  great  merit  of  having  given  us  a  good, 
practical  process,  so  perfect  that  it  has  not 
been  improved. 

We  will  first  give  a  succinct  description  of 
the  chemical  actions  occuring  in  the  intensifi- 
cation of  negatives,  then  explain  the  modus 
operandi. 


INTENSIFICA  TION. 


109 


Mercuric  chloride  {bichloride  of  mercury , 
corrosive  sublimate )  occurs  crystallized  in 
colorless  rhombic  needles  witliout  water  of 
crystallization.  Its  taste  is  styptic,  its  reaction 
acid.  It  dissolves  in  15  parts  of  water  at 
10°  C,  in  two  and  one-half  parts  of  alcohol, 
and  four  parts  of  ether.  It  is  very  toxic.  At 
the  dose  of  from  3  to  5  grains  it  causes  death. 
Albumen  is  the  best  antidote.  In  moist  air 
and  under  the  influence  of  light  it  is  slowly 
decomposed  into  mercurous  chloride ;  oxygen 
is  given  off  and  hydrochloric  acid  formed. 

Sodium  thiosulphate  converts  it  into  sul- 
phide : 

HgCl2+Na2S203+H20=HgS+Na2S04+2  HCl. 

Ammonia  throws  down  a  white  precipitate 
consisting  of  mercurammonium  chloride  : 

HgCl2+2  NH^OH^NH^Cl+NH^HgCl-f  2  HA 

Silver  immersed  in  a  solution  of  mercuric 
chloride  first  blackens,  then,  in  a  certain 
period,  a  grayish-white  deposit  of  mercurous 
chloride  is  formed  on  its  surface  : 


Ag2+2  HgCl,=Hg,Cl,+2  AgCl. 


no  THE  PHOfOOttAPHtC  IMA GK 


Mercurous  chloride  {calomel)  is  an  insoluble 
white  substance  without  taste  and  odor.  In 
the  light  it  turns  yellow,  then  grey  from  a 
partial  decomposition  into  mercury  and  mer- 
curic chloride.  Ammonium  nitrate  dissolves 
it,    It  is  not  poisonous. 

Treated  by  ammonia  it  is  transformed  into  a 
black  insoluble  compound,  mercurous  ammo- 
nium chloride : 

Hg2Cl2+2  NH,OH=NH2Hg2Cl+NH,Cl 
+2  H2O. 

Ammonium  carbonate  gives  rise  to  a  similar 
action : 

Hg2Cl2  +  (NH4)2C03=NH2Hg2Cl+NH,Cl+H20 
+CO2. 

Sodium  thiosulphate  converts  it  into  a  black 
substance,  Hg2S,  soluble  in  aque  regia  and 
resolved  by  heat  into  mercuric  sulphide  and 
mercury : 

Hg^^l2+NaA03+H20=Hg2S^-Na2SO,+2HCl. 

Sodium  sulphite  precipitates  mercury  : 
Hg2Cl2+Na2S03+H20=Hg2+Na2S04+2HCl. 


INTENSIFICATION. 


Ill 


Ammonium  sulph-hydrate  (ammonium  sul- 
phide) converts  it  into  mercuric  sulphide  : 

Hg2Cl2+2  NH,S=2  HgS+2  NH.Cl. 

Treated  by  potassium  ferrous  oxalate  it  is 
reduced  to  metal : 

Hg2Cl2+2  reC20,+KA04=re2(C204)3 
+2  KCl+Hg2.* 

The  cliches  are  intensified  when  fixed  and 
dry.  They  should  be  free  from  yellow  fog  and 
especially  from  all  traces  of  sodium  thiosul- 
phate  which  by  reacting  with  mercuric  chloride 
stain  the  film  brown.  When  this  happens,  the 
cliche  must  be  treated  by  a  very  diluted  solu- 
tion of  ammonium  sulph-hydrate  to  convert 
the  silver  forming  the  image  into  silver  sul- 
phide. This  done,  the  'film  should  be 
thoroughly  washed.  As  a  certain  amount  of 
intensification  results  from  this  treatment 
it  should  be  taken  into  account.  Another  essen- 
tial precaution  is  to  immerse  the  cliche  in 
water  for  a  few  minutes  before  intensifying  in 

*  See  my  paper  on  **  The  Chemistry  of  Mercury  and 
its  Salts,  and  Their  Behavior  in  Photography,"  in 
Anthony's  Phot.  Bull.,  Vol.  XX,  pp.  620  ctaeq. 


112 


THE  PHOTOGRAPHIC  IMAGE. 


order  to  soften  the  film  and,  after  the  treat- 
ment by  mercuric  chloride,  to  well  wash  off 
this  salt,  for,  as  said  above,  it  forms  with  am- 
monia a  white  insoluble  precipitate  which 
would  be  retained  in  the  film. 

Various  degrees  of  intensification  can  be 
obtained  by  the  mercury  process  and,  in  fact, 
by  any  other  one.  To  that  end,  the  chemical 
actions  being  rapid,  one  should  operate  with 
weak  solutions,  say  2  or  3  of  mercuric  chloride 
for  100  parts  of  water. 

On  the  application  of  mercuric  chloride  the 
image  first  blackens  from  the  formation  of 
mercury  oxide  and,  under,  the  amalgamation 
of  the  silver.  If  the  action  be  then  stopped, 
the  film  washed,  then  treated  by  a  very  diluted 
solution  of  ammonia  or  of  ammonium  car- 
bonate— we  prefer  the  latter — the  minimum  of 
intensification  is  obtained. 

But  if  the  action  is  allowed  to  go  on,  one 
observes  by  examining  the  cliche  from  the 
back  that  the  half  tints,  being  formed  by  a 
thin  layer  of  metalic  silver,  are  first  bleached 
through  from  formation  of  mercurous  chloride, 
while  the  high  lights  are  only  partly  acted  on, 


INTENSIFICA  TION. 


113 


that  is,  superficially  covered  by  a  deposit  of 
the  same,  Hg2Cl2.  Therefore  if  the  chemical 
action  is  stopped  at  this  second  stage  the 
intensification  will  be  greater  in  the  half  tints 
than  in  the  high  lights  when  the  film  is  treated 
by  ammonia  or  any  other  reagent.  But  were 
the  whole  silver  converted  into  silver  chloride, 
then  the  layer  of  mercurous  chloride  being 
greater  in  the  high  lights,  the  intensity  of  the 
latter  would  be  in  proportion  more  opaque 
than  in  the  half  tints  and  the  contrasts  of  the 
image  would  necessarily  be  increased. 

The  operation  should,  therefore,  be  con- 
ducted according  as  whether  it  is  necessary  to 
increase  the  general  intensity  or  the  opposi- 
tions between  the  local  intensities. 

When  the  image  is  uniformly  bleached 
through,  it  is  still  possible  to  modify  the 
intensification.  It  suffices  to  employ  a  dilute 
solution  of  the  reagent  which,  by  acting  grad- 
ually, produces  the  necessary  change  in  the 
parts  where  the  mercurous  chloride  is  in  a 
thinner  layer — the  half  tints — before  acting 
through  the  whole  mass  formed  in  the  high 
lights.  It  must  be  admitted  that  the  latter 
action  is  not  very  well  under  control. 


114 


THE  PHOTOGRAPHIC  IMAGE. 


Sodium  thiosulphate,  5 : 100,  is  seldom 
selected,  if  ever,  to  blacken  the  mercurous 
chloride  on  account  of  the  prolonged  washing 
required  to  eliminate  it  from  gelatine  films. 
If  employed  it  should  be  in  very  diluted  solu- 
tion in  order  not  to  dissolve  the  silver 
chloride,  and  thereby  to  lessen  the  opacity.* 

A  weak  solution  of  aqueous  ammonia  is 
generally  preferred. t 

Aqueous  ammonia,  26°  Baume   .      .     5  parts. 
Water   100  " 

or — 

Sesqui carbonate  of  ammonium   ,      .    10  parts. 
Water  100  *' 

The  intensification  by  sodium  sulphite, 
3  : 100,  is  not  very  opaque  and  allows  a  rapid 
printing.    If  the  sulphite  solution  is  almost 

*  See  Professor  Ad.  Martin's  process. 

t  Soue  authors  state  that  the  silver  chloride  mixed 
with  the  mercurous  chloride  is  dissolved  by  ammonia. 
It  is  true  that  aqueous  ammonia  dissolves  AgCl,  but  at 
the  concentration  it  is  here  employed  the  solution  is  too 
feeble  for  that  purpose,  very  little  if  any  is  dissolved. 

Other  authors  recommend  to  dissolve  AgCl,  stating 
that  it  will  blacken  under  the  influence  of  light.  That  is 
an  error.  Silver  chloride  intimately  united  to  calomel 
is  insensitive  to  light, 


INTENSIFICA  TION. 


115 


saturated  by  the  silver  salt  the  intensity  is 
much  increased. 

The  intensification  by  the  above  reagents  is 
rapid.  That  with  a  ferrous  oxalate  developer 
acting  gradually  on  the  mercurous  and  silver 
chloride  which  it  reduces  to  the  metallic  state 
is,  therefore,  better  under  control.  The  modus 
operandi  suggests  itself.  It  is  a  redevelop- 
ment, so  to  speak,  and  succeeds  well  if  the 
plate  is  allowed  to  dry  before  proceeding, 
otherwise  the  intensification  would  very  likely 
be  irregular. 

The  oxalate  solution  can  be  compounded  as 
follows : 

Saturated  solution  of  potassium  oxalate  .    30  parts, 
"  ferrous  sulphate   .     5  ** 

Tartaric  acid  1  part, 

Water  20  parts. 

No  bromide. 

Thir,  excellent  process,  due  to  Mr.  A. 
Chardon,  bears  a  strong  resemblance  with  that 
devised  years  ago  by  Thomas  Sutton  for  inten- 
sifying with  an  alkaline  pyrogallol  developer 
the  cliches  on  collodion  bleached  by  mercuric 
chloride.  In  fact,  all  the  developers  for  dry 
plates  can  be  employed  in  weak  solutions 


116 


THE  PHOTOGRAPHIC  IMAGE. 


provided,  as  previously  said,  the  cliche  treated 
by  the  mercuric  salt  or  any  other  agent  be 
allowed  to  dry  before  being  intensified. 

When  the  image  is  weak  and  veiled,  yielding 
prints  without  vigor,  contrasts  are  obtained  by 
treating  it  after  fixing  and  rinsing  with  a 
solution  of — 

A.mmonium  sulphocyanate  .      .     10  parts. 
Gold  terchloride,  1 : 100,      .     .     10  *« 
Water  100 

"When  the  desired  effect  is  produced  it  suf- 
fices to  wash  thoroughlyo 

For  white  and  black  images  (copies  of  pen 
and  ink  drawings,  engravings,  etc.^)  the  follow- 
ing methods  should  be  employed  to  obtain 
opaque  intensities : 

Carey  Lees  Process,  The  negative  is  fixed, 
carefuPy  washed  and  then  treated  by  an  iodine 
solution  t  until  the  films  become  yellow.  The 

*  The  plates  we  recommend  for  copying  such  subjects 
are  "  Carbutt's  Process  Plates."  None  surpasses  them. 
However,  cliches  on  collodion  are  preferable  for  photo- 
engraving. 

t  Iodine  2,  potassium  iodide  5,  water  480. 


INTENSIFICA  TION. 


117 


plate  is  afterwards  washed  and  flowed  with 
the  following  solution : 

Crystals  of  Schipp's  salt  (sulphantimonate 


of  sodium)  1  part, 

Water  12  parts. 

or — 

Filtered  solution  of  the  salt  .      .     1  part, 
Water  8  parts. 


Under  this  treatment  the  reduction  assumes 
shades  varying  from  russet  to  scarlet  accord- 
ing as  the  yellowness  of  the  cliche  is  more  or 
less  pronounced. 

The  Schipp's  solution  gradually  decomposes. 
By  adding  to  it  a  little  liquid  ammonia  (about 
1|  p.  100)  it  keeps  well. 

Preparation  of  the  salt : 


Grey  sulphide  of  antimony     .      .  22  parts. 

Sodium  carbonate  cryst.  .     .     .  44  " 

Well  burnt  lime   17 

Flowers  of  sulphur    .      .      .      .  4  '* 

Water   48  " 


The  lime  is  first  slaked  in  the  water  and  140 
parts  more  of  water  is  added  together  with  the 
other  ingre(Jients.  Boil  until  the  sulphide  has 
become  white,  filter  and  crystallize.  It  is, 
however,  unnecessary  to  take  the  trouble  of 


118  THE  PHOTOGRAPHIC  IMAGE. 


crystallizing  as  the  solution  can  be  used  as 
said  above. 

The  chemical  changes  consists  in  the  trans- 
formation of  the  silver  iodide  into  silver 
sulphantimonate,  thus  : 

6  AgI+3  Na^S.Sb^Os^S  Ag2S.Sb205+6  Nal." 

If  the  cliche  is  bleached  by  mercuric 
chloride  instead  of  iodine,  the  intensity  is 
greater  from  formation  of  mercurous  and 
argentic  sulphantimonates.  Mercurous  sul- 
phantimonate is  orange  and,  as  in  the  iodine 
process,  the  argentic  salt  is  brownish-black, 
turning  brown  as  it  dries.  The  changes  with 
mercurous  chloride  are  as  follows : 

3  Hg2Cl2+3  Na2S.Sb205==3Hg2S.Sb205+6  NaCl. 

H.  Belle's  Process.  Prepare  a  solution  of  sul- 
phate of  uranium  and  another  of  potassium 
ferricyanate,  both  of  the  same  strength,  about 
1  : 10.  Mix  them  by  equal  volumes  in  such 
a  quantity  as  may  be  required  for  one  or  two 
days'  use,  and  pour  the  mixture  on  the  fixed 
and  well  washed  cliche  :  the  silver  is  trans- 
formed into  ferrocyanate  and  a  brown  precip- 
itate of  uranium  ferrocyanate  is  deposited. 


INTENSIFICA  TION. 


119 


The  intensification  proceeds  as  long  as 
necessary,  and  this  without  sensibly  increasing 
the  deposit,  thus  securing  delicacy  of  details. 

Instead  of  mixing  the  two  salts,  as  recom- 
mended by  Mr.  Selle,  it  is  best  to  first  treat 
the  negative  with  the  uranium  solution  at  1 
per  100,  then  to  add  to  it  a  few  drops  of  the 
ferricyanate  solution,  3 : 100,  and  pour  back 
the  whole  on  the  cliche  until  the  desired  effect 
is  produced. 

Cliches  intensified  by  this  process  become 
more  and  more  intense  in  the  light  and  worth- 
less if  the  image  is  in  half  tones.  By  heating 
them  over  an  alcohol  lamp  the  opacity  can  be 
somewhat  reduced. 

The  following  equations  show  that  it  is  a 
sine  qua  non  to  use  uranic  salts,  sulphate  or 
nitrate  of  uranyl. 

By  mixing  the  ferricyanate  and  the  uranic 
salt,  uranic  ferricyanate  is  formed  : 

3  (UO2)  (N03)2+  KeFe^Cy.^  =  (UO,)sFe,Cj,, 
+6  KNO3; 

then  this  salt  produces  the  changes  in  question : 

Ag,+2  (U0,)3  F6,Cy,,=Ag.FeCya 
-4-2  {VO,),-FeCj,. 


120 


THE  PHO  TO  G  RA  PHIC  IMA  GE. 


By  treating  the  cliche  thus  intensified  with 
aluminum  chloride,  1 : 10,  the  color  turns  to 
an  olive  brown.  With  gold  terchloride  it  is 
changed  into  a  violet  or  emerald  green,  and 
black  or  olive-black  by  platinum  tetrachloride: 

(U02)2FeCy6+PtCl4=PtFeCy6+2  (U02)Cl2* 

These  chemical  actions  are  often  employed 
to  tone  diapositives,  etc. 

Dr,  J,  3£  Eder's  Process.  After  treating 
tjie  cliche  by  mercuric  chloride  and  washing, 
it  is  immersed  in  a  solution  of — 

Potassium  cyanide,  pure    .     .     2  parts, 
Potassium  iodide  ....     1  part, 
Mercuric  chloride  .     .     .     .     1  *♦ 
Water  420  parts. 

In  this  the  cliche  first  turns  yellow,  then 
gradually  to  coffee-color,  and  then  to  chocolate- 
brown.  At  this  stage  the  color  commences  to 
lighten,  assuming  various  tints  without  losing 
any  details,  and  the  cliche  becomes  more 
transparent.  If  the  action  does  not  reach  the 
brown  color  more  cyanide  should  be  added. 

*  See  our  papers  on  the  Chemistry  of  the  Salts  empoyed 
in  Photography  in  Anthony's  Phot.  Bull.,  Vols.  XX  and 
XXI. 


INTENSIFICA  TION. 


121 


Generally  tlie  intensifying  is  stopped  at 
some  of  the  stages  of  the  reversal  of  the  action, 
that  is,  when  the  color  lightens. 

The  same  solution  can  be  employed  to 
reduce  the  intensity  of  cliches,  leaving  out  the 
previous  treatment  with  mercuric  chloride. 
The  action  is  slow  and  regular.* 

Intensification  with  silver.  Although  the  in- 
tensification with  silver  is  the  most  rational 
and  the  cliches  intensified  by  mercury  liable  to 
fade,  and  those  strengthened  by  uranium  to 
intensify  by  exposure  to  light,  we  do  not 
advise  it.  It  is,  on  the  whole,  a  risky  opera- 
tion, liable  to  stain  the  cliche  even  when  every 
trace  of  sodium  thiosulphate  is  eliminated. 

To  insensify  by  this  process  the  cliche  is 
immersed  in  water  to  soften  the  film,  then  for 
a  moment  in  a  solution  of  citric  acid  at  2  per 
100,  then  placed  until  the  proper  intensity  is 
obtained  in  one  of  the  following  developers  to 
which  have  been  added  a  few  drops  of  a  5  per 
100  solution  of  silver  nitrate  : 

*  The  intensification  is  due  to  t'n«  formation  of  Hgglj 
whose  color  varies  as  the  action  proceeds  and  this  salt  is 
gradually  dissolved  by  potassium  cyanide  when  the  first 
reaction  is  complete. 


122  THE  PHOTOGRAPHIC  IMAGE. 


1.  Gallic  acid    ...  1.  part, 
Acetic  acid  No.  8      .  6.  parts. 
Water     ....  100.  " 

or — 

2.  Hydroquinone     .     .  2.  parts. 
Water     ....  100.  « 
Nitric  acid    ...  0.1  part. 

After  this  treatment  tlie  cliclie  slioiild  be 
washed,  fixed,  &c. 


CHAPTER 


VI. 


Eeduction  of  Intensity. 


The  cliclies  can  be  too  intense  *.om  three 
causes,  viz. :  1st,  Yellow  fog ;  2nd,  General 
intensity  too  opaque ;  3rd,  The  high  lights  too 
intense  from  short  exposure-time  or  the  devel- 
opment not  having  been  well  conducted. 

1st. — Yellow  fog  is  prevented  by  immersing 
the  cliche  before  fixing  in  a  "clearing  solution" 
consisting  of — 

Hydrochloric  acid    .     .  1  part, 

Water   20  parts. 

or — 

Citric  acid  .     ,     .     .  2  parts. 

Water  .     .     .     .     .  20  " 

Mr.  B.  J.  Edwards  advises  to  change  the 
yellow  color  of  the  fixed  cliche  into  one  per- 
mitting to  print  more  rapidly.     For  that 


124  THE  PHO TOGRAPHIC  IMA  GE. 


purpose  he  places  the  cliche  for  a  few  minutes 
in  a  solution  of — 

Alum  1  part,* 

Citric  acid  .     .     .     .     1  ** 
Ferrous  sulphate    .     .     3  parts. 

Water   20 

By  treating  the  cliche  after  fixing  and  wash- 
ing with  the  following  compound,  the  yellow 
color  is  changed  into  one  of  steel  grey  : 

Oxalic  acid     ...      1  part, 
Water  30  parts. 

According  to  Mr.  A.  Chardon,  yellow  and 
green  fogs  are  removed  without  any  alteration 
in  the  intensities  of  the  cliches  by  a  neutral 
or,  more  effectually,  a  slightly  alkaline  solution 
of  ammonium  citrate  1 : 50. 


2nd. — The  three  processes  following  are 
usually  employed  to  reduce  the  intensity  of  a 
cliche  in  which  the  general  intensity  is  too  opaque. 
They  are  known  as  the  Spiller,  Monckhoven, 
and  Farmer's  processes.  We  prefer  the  former 

*  Alum  is  not  useful  to  remove  yellow  fog.  We 
discard  it  unless  the  acid  solution  produces  blisters,  etc. 
See  "Causes  of  Failures." 


REDUCTION  OF  INTENSITY,  125 


because  no  sodium  thiosulphate  being  em- 
ployed, the  after-wasliing  is  more  easily  and 
effectually  done,  and  no  injurious  compound 
is  left  in  the  film. 

Spiller's  Process.  "  The  process  which  I  now 
proceed  to  describe,"  says  Professor  John 
Spiller,  "  answers  perfectly,  for  it  can  be  held 
completely  under  control,  be  made  to  reduce 
the  image  at  any  required  rate,  working 
regularly  and  uniformly  without  any  mottling 
and,  at  the  same  time,  hardening  the  film  so 
that  it  can  be  rubbed  with  the  hand  to  assist 
the  removal  of  any  surface  stains,  and  never 
once  have  I  observed  any  trace  of  frilling. 

Stock  Solution  A  is  made  up  of — 

Alum  1  part, 

Copper  sulphate      .     .     1  *' 
Common  salt     ...     2  parts.^ 

Water  10 

Dissolve  together  and  filter. 

Solution  J5  is  a  cold  saturated  solution  of  common 
salt,  filtered. 

"  For  ordinary  use,  mix  A  and  B  in  equal 
volumes,  and  immerse  the  negative  therein. 
In  obstinate  cases,  employ  more  of  the  copper 


126  THE  PHOTOGRAPHIC  IMAGE. 


solution.  When  tiie  required  degree  of  reduc- 
tion is  attained,  rinse  with  fresh  salt  brine  and 
wash  well  with  water  to  remove  all  the  soluble 
salts. 

"The  chemical  action  is  practically  the  attack 
of  metallic  silver  with  cupric  chloride  to  form 
a  double  argentic  and  cuprous  chloride,  which 
is  soluble  in  salt  brine,  the  alum  being  added 
only  for  the  purpose  of  hardening  the  gelatine 
film,  thus  : 

CuCl2+Ag=CuCl+AgCl. 

"Changes  of  color  will  be  observed;  but 
watch  well  the  altered  intensity,  and  stop  as 
soon  as  the  desired  stage  has  been  reached. 
Always  wash  well  in  the  salt  brine  to  remove 
the  copper,  and  finish  under  the  tap,  or  in  a 
few  changes  of  water. 

"A  chemist  will  understand  that  a  mixture  of 
blue  vitriol  and  common  salt  is  equivalent  to 
cupric  chloride  and  sulphate  of  soda,  as 
denoted  by  the  change  of  color  from  blue  to 
green  when  making  up  the  solution,  and  in 
cold  weather  some  of  the  sulphate  of  soda 
usually  crystallizes  out."  * 


*  Year  book,  1884,  p.  67,  et  seq. 


REDUCTIOJ^  OP  IN  TENS  IT  F. 


127 


Br.  Monchoveris  Process  (1882).* 

Potassium  ferric  oxalate   .    15  to  20  parts. 
Sodium  thiosulphate    .     .     .  60 
Water   480  " 

In  this  process  the  reduction  is  effected  by 
sodium  thiosulphate  dissolving  the  silver 
oxalate  formed : 

Ag2+re2(C20,)3=Ag2CA+2  FeCA 
then — 

Ag2C204+2  Na2S203=2  AgNaS203+Na2C204. 

Wm.  Willis,  the  inventor  of  the  platinotype, 
has  utilized  the  former  action,  that  is,  the 
transformation  of  silver  into  oxalate,  to  the 
intensification  of  negative  cliches  by  treating 
the  bleached  image,  Ag2C204,  by  a  ferrous 
oxalate  or  an  alkaline  pyrogallol  developer 
(1882). 

Mr.  E.  Howard  Farmer's  Process,  "  Pre- 
pare a  solution  of  ferricyanate  of  potassium  by 

*  This  process  is  often  recommended  to  clear  the  lines 
in  white  and  black  negative  cliches.  We  prefer  a  simple 
wash  with  an  alcoholized  solution  of  potassium  cyanide 
chemically  pure,  if  possible,  on  account  of  the  great 
quantity  of  carbonate  the  commercial  article  contains. 


128  THE  PHOTOGRAPHIC  IMAGE. 


dissolving  one  part  of  the  salt  in  sixteen  parts 
of  water.  To  reduce  the  intensity  immerse 
for  a  few  minutes  the  negative  in  a  solution  of 
sodium  thiosulphate  1 : 16,  and  then  add  to  this 
a  few  drops  of  the  ferricyanate  solution.  A 
gradual  reduction  will  take  place  without 
change  of  color,  the  rapidity  depending  on  the 
quantity  of  ferricyanate  added.  When  suffi- 
ciently reduced,  wash  well  the  negative. 

"  To  reduce  locally,  immerse  the  plate  in 
water  for  a  few  minutes  and  apply  the  mixed 
solution  with  a  camel-hair  brush  or  pellet  of 
cotton-wool  to  the  parts  required ;  there  is  no 
fear  of  markings. 

*'  To  remove  silver  stains,  etc.,  on  the  nega- 
tive, immerse  it  in  water,  rub  over  with  a 
pellet  of  wool  which  has  been  dipped  in  the 
solution,  and  rinse  under  the  tap  before  the 
solution  has  time  to  diffuse  into  the  film. 

"  The  solution  is  also  efficacious  with  over 
dense  silver  prints."  * 

By  this  process  the  cliche  can  be  reduced 
just  after  fixing  and  rinsing.  When  the  cliche 
is  a  portrait  which  should  be  retouched  it  is 


*  Year  book,  1884,  p.  59,  et  seq. 


REDUCTION  OF  INTENSITY.      "  129 


advisable  to  harden  the  film  by  immersing  th^ 
plate  for  a  moment  in  a  solution  of  borax  at  6 
per  100  of  water.* 

The  rationale  of  this  process  is  very  simple : 
the  ferricyanate  transforms  the  metallic  silver 
into  ferrocyanate  soluble  in  sodium  thiosul- 
phate : 

Ag4+2  KeCFe^Cyi^)  =  Ag,(reCye)+3  K,(reCye). 

The  mixture  of  the  two  salts  does  not  keep. 
The  following  solutions  can  be  prepared  before- 
hand and  mixed  by  equal  volumes  for  use. 

A.  Potassium  ferricyanate    .     .      1  part, 
Water  240  parts. 

B.  Sodium  thiosulphai*  ...     40  parts. 
Water   240  " 

In  these  processes  the  intensity  is  reduced 
by  dissolving  the  metallic  silver  forming  the 
image.  Employed  to  lighten  good  cliches 
over  developed,  that  is,  whose  intensity  is  too 
opaque  in  all  the  parts  of  the  picture,  the 
relative  value  of  the  local  intensities  is  little 
altered  provided  the  operation  be  conducted 

*  Borax  can  replace  alum  to  harden  the  film  in  most 
cases. 


130  THE  PHOTOGRAPHIC  IMAGE. 


with  great  care.  Otherwise  it  may  happen — 
and,  indeed,  this  is  of  frequent  occurrence — 
that  the  half  tints,  being  f /rmed  by  thin 
layers  of  metal,  do  not  stand  the  dissolving 
action  and  are  washed  off,  th^is  impairing  the 
beauty  of  the  image  past  remedy. 

A  more  rational  and  safe  method  would  be  to 
change  the  color  of  the  cliche,  or  to  render  the 
reduction  more  transparent,  so  that  the  only 
desired  change  would  be  produced,  but  if  the 
intensity  was  too  much  reduced  it  would 
always  be  possible  to  strengthen  it  again  by 
an  exceedingly  weak  developer  well  restrained. 

For  example  :  The  cliche  previously  soaked 
in  water  is  immersed  for  a  certain  period  in 
an  aqueous  solution  of  bromine  to  partly 
transform  the  metallic  silver  into  bromide. 
Under  this  treatment  the  image  seems  to 
intensify  on  account  of  the  opaque  yellowish- 
white  silver  bromide  formed,  but  when  exposed 
for  a  certain  period  to  sunshine  it  becomes 
more  transparent  from  the  reduction  of  the 
silver  salt  which  turns  to  a  bluish  violet-black. 

The  operation  should  be  made  by  diffused 
light  and  the  cliche  not  exposed  to  the  sun's 
light  until  quite  dry,  otherwise  the  silver 


REDUCTION  OF  INTENSITY.  131 


bromide  reduction  would  be  of  unequal  in- 
tensity and  lighter  in  the  parts  drying  first. 
In  fact,  when  the  cliche  is  exposed  to  the 
luminous  action  under  water  and  in  presence 
of  an  absorbent  of  the  haloid  the  reduction  is 
always  much  darker. 

If  the  cliche  be  thoroughly  bleached,  it  is 
necessarily  much  weakened,  too  much  so,  gen- 
erally ;  but  various  remedies  are  at  hand.  It 
may  be  intensified  after  insolution  by  a  weak 
alkaline  developer,  by  mercuric  chloride,  pal- 
ladious  chloride,  etc. 

Similar  results  are  obtained  in  treating  the 
image  with  a  weak  solution  of  ferric  chloride 
very  little  acidified  with  citric  acid.  When  the 
desired  effect  is  produced,  the  cliche  should 
be  rinsed  in  a  2  : 100  solution  of  citric  acid,  then 
washed  to  eliminate  all  traces  of  the  iron  salts 
before  proceeding. 

No  fixing  is  required  after  any  one  of  these 
treatments ;  it  suffices  to  well  wash  in  the 
ordinary  way. 

If  the  cliche  is  too  intense  in  the  lights j  yielding 
harsh  positive  impression,  as  it  happens  when  the 
development  is  badly  conducted,  or  pushed  to  obtain 


132  THE  PHOTOGRAPHIC  IMAGE. 


t!ie  details  in  case  nf  manifest  short  exposure- 
times,  or  wlien  the  developer  contains  too  great  a 
quantity  of  bromide,  the  image  should  be  trans- 
formed into  silver  chloride  or  bromide,  then 
after  washing,  treated  by  a  weak  ferrous 
oxalate,  pyrogallol  or  hydroquinone  developer, 
taking  care  to  stop  the  development  before  the 
layer  of  the  haloid  «alt  in  the  high  lights  be 
reduced  through,  whereby,  after  fixing,  the 
cliche  will  present  less  contrasts  than  before 
this  treatment. 

The  solutions  to  transform  the  silver  into 
chloride  or  bromide  are  the  following : 


A.  Ferric  chloride   10  parts 

Hydrochloric  acid     ....  5  " 

Water   480 

or — 

B.  Iron  bromide   10  parts. 

Nitric  acid    ...      .     .     .  5  " 

Water   480  " 

Cliches  intensified  with  mercury  are  re- 
duced by  potassium  cyanide : 

Potassium  cyanide,  CP.     .     .     5  parts. 

Water  120 

Alcohol       ......    30  " 


Seme  operators  employ  this  solution  to 
reduce  the  general  intensity. 


CHAPTER  VII. 


Causes  of  Failuees. 


I.  Fogging  or  a  reduction  of  silver  over  the 
whole  film  veiling  the  image. — It  may  occur  from 
developing  over  exposed  plates  with  a  devel- 
oper strong  in  alkali  and  not  restrained  ;  or, 
from  pushing  the  development  by  over  doses 
of  the  same ;  or,  by  prolonged  development 
with  concentrated  developing  solutions,  and 
from  the  bad  quality  (actinism)  of  the  light  in 
the  dark  room. 

For  plates  which  fog  from  a  bad  preparation 
of  the  emulsion  there  is  a  "certain  cure," 
which  consists  of  immersing  the  plate  in  a  two 
per  cent  solution  of  potassium  bichromate  for 
about  an  hour  and  then  washing  out  the 
bichromate  with  extreme  care.  "  The  sensi- 
tiveness after  this  treatment  is  not  mucui 


134  THE  PHOTOGRAPHIC  IMAGR 


diminislied,  and  the  negatives  taken  with  (the 
plates)  are  beautifully  bright."^ 

Plates,  gelatine  or  dry  collodion,  having 
been  accidently  struck  by  light,  or  exposed 
in  the  camera,  can  be  treated  in  a  similar 
manner  to  destroy  the  luminous  impression, 
and  then  yield  good  results  although  the 
sensitiveness  is  to  a  certain  extent  impaired. 
The  process  consists  to  immerse  the  plate  in 
the  following  solution  for  a  period  of  from 
10  to  15  minutes ;  then,  after  a  thorough 
washing,  to  let  them  dry  spontaneously  in 
taking  the  usual  care 

Potassium  bichromate  .     .     3  parts. 
Hydrobromic  acid       .     .    10  " 
Water   480  " 

The  sensitiveness  of  the  plates  so  treated 
can  be  exalted  by  immersing  them  for  a  minute 
in  a  weak  solution  of  hydroquinone,  drying,  &c. 

II.  Frilling  and  blistering. — Too  much  alkali 
in  the  developing  solution,  especially  when 
employing  the  caustic  alkalies ;  fixing  solution 
too  concentrated ;  long  washing — tepid  water 
softens  the  gelatine  and  causes  it  to  swell,  and 
as  the  support  is  rigid  the  film  blisters  and 

*  Abney. 


CAUSES  OF  FAILURES. 


135 


tends  to  detatch  itself  from  the  plate,  hence 
the  defect. 

If  it  occurs  during  the  development  it  is 
prevented  by  soaking  the  plate  before  develop- 
ing in  a  solution  of  Epson  salt,  1  : 8,  for  a 
minute,  and  rinsing.  Coating  the  gelatine 
film  with  plain  collodion  is  an  effective  remedy 
recommended  by  Captain  Abney. 

The  defects  are  now  seldom  met  with. 
However,  it  is  well  during  the  warm  season  to 
use  cold  water,  15°-20^  C,  and  to  insolubilize 
the  film  after  developing  by  immersing  the 
the  plate  for  a  few  minutes  in  a  solution  of 
borax  or  of  chrome  alum.  Edging  the  film  with 
wax  dissolved  in  benzine  or  with  tallow  before 
developing  is  a  good  preventative  for  the  edges. 

The  solutions  of  acids  (hydrochloric,  sul- 
phuric, etc.)  employed  to  destroy  yellow  fog,  or 
for  other  purposes,  have  a  tendency  to  produce 
blisters  and  frilling.  This  is  avoided  by 
adding  chrome  alum  to  these  solutions,  about 
5  per  100,  the  alum  exerting  a  tanning  action 
also  useful  to  prevent  by  time  the  decomposi- 
tion of  gelatine  (mouldiness)  by  the  germs  from 
the  air  growing  in  presence  of  moisture  and 
organic  matters 


136 


THE  PHOTOGRAPHIC  IMAGE. 


III.  Flatness, — Normal  exposure  :  The  de- 
velopment was  conducted  to  obtain  the  details 
as  it  is  proper,  but  without  afterwards  pushing 
to  intensity.  Over  exposure  :  The  develop- 
ment has  not  been  conducted  to  obtain 
intensity  before  or  simultaneously  with  the 
details. 

IV.  Negatives  wanting  in  details. — Develop- 
ing solution  too  strong  and  rapidly  inten- 
sifying. 

Pushing  to  intensity  when  the  details  are 
not  sufficiently  developed. 
Real  under  exposure. 

V.  Negatives  ivealc,  details  good. — The  devel- 
opment stopped  before  the  general  intensity 
is  obtained. 

The  negatives  can  be  intensified  by  the 
mercuric  process. 

YI.  Negatives  generally  too  intense.  —  Over 
development.* 

VII.  Negatives  strong  and  yielding  harsh^ 
white  and  hlach  impressions. — The  development 
pushed  to  obtain  the  details  in  the  shadows 


*  ^ee  the  reducing  processei?. 


CAUSES  OF  FAILURES. 


137 


when — the  exposure  being  very  short — they 
should  have  been  sacrificed  to  preserve  the 
gradations  in  the  lights,  etc. 

The  development  conducted  with  too  much 
pyrogallol  to  begin  with. 

VIII.  The  image  develops  slowly  and  with 
abnormal  contrasts,  although  the  exjjosure-time  is 
correct. — This  defect  occurs  when  using  the 
same  developing  solution  over  again. 

No  doubt  the  reductive  power  of  developing 
solutions  is  not  exhausted  by  a  single  opera- 
tion and  that  several  plates  can  be  successively 
developed  in  the  same  solution.  But  whether 
the  results  are  equally  as  good  or  similar  is  a 
question,  for  each  operation  not  onl^^  lessens 
the  reductive  power  but  also  originates  a 
restraining  action  due  to  a  certain  quantity  of 
an  alkaline  bromide  formed  by  the  reduction 
of  the  corresponding  silver  salt.  Hence  a 
longer  exposure  is  required,  and  it  does  not 
even  counteract  the  restraining  action  and 
compensate  for  the  want  of  energy  of  the 
developer  which  acts  more  and  more  slowly, 
the  contrasts  increasing  ana  the  image  finally 
refusing  to  develop,  except  in  the  high  lights. 


138  THE  PHO TOGRAPHIC  IMA  QE. 


The  addition  of  more  alkali  and  of  the  reagent 
does  not  satisfactorily  remedy  these  defects. 

A  developer  should  be  used  to  develop,  I 
will  not  say  only  one  cliche,  but  no  more  than 
three  and  this  in  large  solutions  and  when  the 
same  results  are  desirable. 

For  portraits  a  new  solution  is  recom- 
mended. 

For  drop-shutter  exposures  it  is  imperative. 

We  have  demonstrated  in  the  preceeding 
pages  that  the  tentative  method  of  developing 
is  the  only  one  rational ;  we  strongly  advise 
the  reader  to  adhere  to  it  in  every  case. 

IX.  Solarization,  —  See  "  Exposure-Time  " 
and  "Introduction." 

X.  Halation,  Irradiation,  Blurring, — A  halo 
or  blurring  at  the  edges  of  the  lights  (blacks) 
and  extending  in  the  shadows  and  sometimes 
in  the  half  lights — often  seen  around  the 
branches  and  upper  parts  of  trees  in  land- 
scapes, the  roofs  of  buildings,  the  windows  in 
parlors,  etc. — occurs  whenever  a  bright  light 
is  in  opposition  to  shadows  or,  white  to  black. 

The  cause  of  this  phenomenon  arises  from 
the  light  being  upwardly  reflected  by  the  back 


CAUSES  OF  FAILURES.  l3d 


of  the  glass  plate.  It  is  so  much  more 
apparent  as  the  exposure-time  is  lengthened. 
Diffraction  is  also  a  cause  of  irradiation.* 

The  reflection  is  prevented  by  backing  the 
plate  with  a  substance  capable  of  absorbing 
the  light  such  as  the  following,  which  is  similar 
to  Gilioris  opaque^  used  for  stopping  skies,  etc. : 

Burnt  sienna,  powdered    .      .    16  parts. 

Dextrine  4  " 

Glycerine       .     .     .     .    2  to  3  ** 
Water      .      .     .       quantity  sufficient. 
These  ingredients  should  be  ground  together  into  a 
thick  paste. 

This  backing  should,  of  course,  be  wiped  off 
before  developing. 

An  excellent  protection  against  hallation  is 
the  coloring  of  the  photo-film  as  first  devised 
by  Mr.  Carey  Lea,  who  advises  coralline  for 
that  purpose  as  not  impairing  the  sensitive- 
ness. 

"  The  result  is  obtained,"  said  Mr.  Lea,t  "  in 
a  simple  manner.    It  is  only  necessary  to  add 

*  On  the  causes  of  halation  see  Abney's  communica- 
tion in  London,  Edinburgh,  and  Dublin  Philos,  Mag., 
May,  January,  1875;  Cornu's  communication  in  Bull. 
Soc.  Franc.  Photo,  1890,  pp.  68,  160,  173;  Davanne  "Pho- 
tographic," Vol.  I.,  p.  165,  Paris,  1886,  Gauthier-Villars. 

t  *' Manual  of  Photography,"  2nd  edition,  new  issue, 
p.  4  of  the  2nd  supplement. 


140 


THE  PHOTOGRAPHIC  IMAGE. 


the  alcoholic  solution  of  coralline  to  the 
finished  emulsion  and  to  employ  it  as  usual.* 
Neither  is  there  any  necessity  of  special 
means  of  removing  the  color  of  the  plate ;  this 
I  would  consider  a  fatal  objection.  Coralline 
has  the  inestimable  advantage  that  it  disap- 
pears by  itself  in  the  operations  of  developing, 
fixing,  and  washing." 

"  The  best  scarlet  coralline  (the  yellow 
coralline  sometimes  called  aurine  is  entirely 
unsuitable)  is  to  be  dissolved  in  alcohol  48 
grains  to  the  ounce.  The  solution  takes  place 
rather  slowly  and  several  days  should  be 
allowed  with  occasional  shaking,  neither  is  it 
ever  entirely  complete,  a  small  amount  of  dark 
residue  always  remains,  even  after  standing 
for  months.  To  each  ounce  of  finished  emul- 
sion from  6  to  10  minims  of  the  coralline 
solution  is  to  be  added  and  well  shaken.  The 
emulsion  is  then  ready  for  immediate  use.  It 
will  not  have  the  strong  red  color  of  corraline, 
but  a  buff  or  salmon  shade." 

*  The  dyed  emulsion  is  sensitive  to  yellow  and  orange. 
It  is  employed  in  orthochromo-photography.  Instead  of 
adding  coralline  to  the  emulsion — collodion  or  gelatine — 
which  is  not  a  sine  qua  non,  the  plate  may  be  dyed  in  the 
usual  manner. 


CAUSES  OF  FAILURES. 


141 


It  is  advisable  to  always  hack  the  plates  when 
working  outdoors  and  photographing  interiors. 

XI.  Transparent  spots;  pin-holes. — Bubbles 
of  air  adhering  on  the  film  during  the  develop- 
ment ;  plates  not  dusted  before  placing  them 
in  the  holder,  etc. 

XII.  Yellow  stains. —  The  developer  much 
oxidized.  Long  development  with  not  enough 
sulphite  or  a  bad  sample  of  it.  This  salt  is 
converted  into  sulphate  in  contact  with  the 
air  and  consequently  becomes  useless.  Yellow 
stains  are  promoted  by  hardening  the  gelatine 
film  with  alum  before  fixing.  They  are  pre- 
vented or  removed  by  the  clearing  solutions."^ 

When  they  are  persistent — which  happens 
when  the  cliche  is  fixed — the  plate  may  be 
treated  by  a  solution  of  JEJau  de  Javelle  or  of 
bleaching  powder ;  or,  after  a  thorough  wash- 
ing, by  a  diluted  solution  of  aqua  regia,  1 : 12, 
as  recommended  by  Prof.  Arthur  H.  Elliott.t 

*  For  formulas  see  "Reduction  of  Intensity,"  Part  II, 
Chap.  VI,  of  this  work. 

t  Aqua  regia  is  prepared  "  by  mixing  six  volumes  of 
hydrochloric  acid  with  one  volume  of  nitric  acid  and 
keeping  the  solution  for  several  days  in  a  warm  place." 
See  Anthony's  Phot.  Bull.,  Vol.  XXI,  p.  98. 


142  THE  PRO  TOGRA  PHIC  IMA  GE. 


We  found  1 : 12  a  strong  solution.  It  soon 
disorganizes  the  gelatine. 

Yellow  fog  often  occurs  in  the  fixing  bath, 
especially  when  hydroquinone  is  used  for 
developing.  The  remedy  is  given  in  the  fol- 
lowing pages. 

XIII.  Crystallizations^    Efflorescence  on  the 
Jflm.  —  The    sodium    thiosulphate    not  well 
washed  out  after  fixing. 

XIV.  Yellowish  stains  on  the  j^lrriy  adherent 
on  the  film,  and  sometimes  embedded. — They 
result  from  not  well  washing  the  developed 
image  before  hardening  the  film  with  alum, 
the  carbonate  or  the  alkali  forming  a  precip- 
itate of  aluminia,  insoluble.*  The  defect  may 
also  be  due  to  the  chemical  action  occurring 
when  sodium  thiosulphate  is  in  presence  of 
alum.  As  a  remedy  wash  the  film  with  acetic 
acid  and  rinse  well. 

A  good  substitute  is  chrome  alum  free  from 
acid. 

XV.  Yellow-hrown  stains  formed  when  intensi- 
fying.—  The  thiosulphate  not   entirely  elim- 


*  By  compounding  the  alum  bath  with  hydrochloric 
acid,  the  defect  in  question  is  avoided.  Beason,  obvious. 


CAUSES  OF  FAILURES. 


143 


inated  by  washing,  or  by  a  chemical  action, 
reacting  with  mercuric  chloride.* 

Mr.  H.  E.  Gunther  states  that  stains  from 
mercuric  intensification  are  removed  by  am- 
monium sulphide.  The  plate  is  for  a  short 
time  placed  into  water,  "  then  sulphydrate  of 
ammonium  (diluted)  is  poured  on  the  plate, 
which  is  done  best  in  the  open  air,  as  the 
liquid  is  a  most  ill-scented  one.  As  soon  as 
this  has  been  done,  the  negative  will  at  once 
be  restored  in  its  original  clearness.  Finally, 
the  plate  must  be  thoroughly  rinsed  and 
washed." 

*  See  "  Fixing,"  Part  II,  Chap.  IV, 


CHAPTER  VIII. 


The  Development  with  Hydeoquinone. 


Hydroquinone  does  Dot  possess  tlie  superior 
and  extraordinary  qualities  which  have  been 
attributed  to  it. 

The  reductive  action  of  pyrogallol  is  more 
energetic  than  that  of  hydroquinone,  the  latter 
requiring  to  be  employed  in  larger  proportions 
and  to  be  compounded  with  greater  doses  of 
alkaline  carbonates,  or  with  caustic  alkalies, 
KOH,  NaOH,  to  increase  the  reductive  action. 

It  does  not  allow  more  latitude  in  the 
exposure-time  than  ^ny  other  reagent ;  and, 
what  13  more  important,  it  does  not  possess 
the  elasticity  of  pyrogallol,  and  the  modifica- 
tions during  the  development,  which  one 
thinks  necessary  to  make  in  the  consti- 
tution of  the  developer  to  produce  certain 
effects,  do  not  much  alter  its  mode  of  action. 


DEVELOPMENT  WITH  HYDROqUINONE.  U5 


The  best  authors  recommend  pyrogallol  for 
this  reason :  it  can  be  made  to  work  in  many 
ways  and  exactly  as  you  please  to  obtain  any 
desired  result. 

The  great  fa^or  which  hydroquinone  finds 
among  amateur  photographers  is  due  to  the 
facility  with  which  it  can  be  used,  and  to  its 
remarkable  keeping  quality  when  compounded 
with  sodium  sulphite,  which  permits  one  to 
prepare  ready-made  solutions  in  which  a 
number  of  images  can  be  developed  one  after 
another  in  a  sort  of  mechanical  manner,  so 
that  photography  has  become  nothing  but  a 
toy  in  the  hands  of  many  would-be  amateurs. 
They  may — in  their  ignorance  of  the  theory  of 
the  process,  the  action  of  each  chemical,  the 
changes  constantly  taking  place  in  the  de- 
veloper— occasionally  produce  very  fine  pho- 
tographs, but  they  generally  obtain  indifferent 
or  bad  ones  :  Rien  de  hlen  ne  se fait  au  hazard. 

It  has  just  been  said  that  the  solution  of 
hydroquinone  and  sodium  sulphite  possesses 
very  good  keeping  qualities ;  but  if  it  remains 
colorless  i:  nevertheless  undergoes  in  a  certain 
period  a  marked  change  in  its  developing 
power*   Mr.  Londe  has  ascertained  by  a  series 


146  THE  PHOTOGRAPHIC  IMAGE. 


of  experiments  tliat  the  alteration  is  quite 
apparent  after  five  days  keeping. 

As  pyrogallol  and  eikonogen,  liydroquinone 
produces  yellow  fog*  by  long  development 
when  the  developer  is  oxidized  to  a  certain 
extent.  It  must  be  admitted,  however,  that 
the  yellow  coloration  can  be  easily  avoided 
and  that  in  ordinary  circumstances  it  yields 
very  clear  cliches,  which  is  certainly  a  very 
great  quality  for  the  reproduction  of  engrav- 
ings, etc.,  and  for  transparencies,  but  which 
for  half  tone,  negatives  may  become  objection- 
able, for  a  slight  veil  all  over  the  cliche  is 
generally  useful  to  prevent  harshness. 

No  doubt  hydroquinone  is  an  excellent 
developer  capable  of  rendering  good  services 
if  properly  managed  and  when  employed  for 
the  development  of  such  subjects  as  those 
which  have  been  alluded  to.  It  is,  for  example, 
the  best  agent  to  be  used  for  diapositives  and 
duplicate  negatives.  The  color  of  the  reduced 
silver  is  fine  and  all  that  can  be  desired  for 
lantern  slides  and  ornamental  transparencies. 

From  the  foregoing  criticisms  we  do  not 

*  An  old  solution  of  hydroquinone  is  exceedingly 
liable  to  produce  'eep  yellow  fog. 


DEVELOPMENT  WITH  HYDROQUINONE.  147 


mean  to  say  that  good  negatives  cannot  be 
regularly  obtained  with  hydro quinone,  but 
simply  that  the  development  cannot  be  so  "Well 
regulated  as  with  pyrogallol,  which  we  con- 
sider the  developei  par  excellence. 

The  development  with  hydroquinone  is  con- 
ducted according  to  the  principles  which  rule 
the  development  with  pyrogallol. 

Generally,  it  is  advisable  to  commence 
developing  with  a  solution  having  but  a 
medium  reductive  energy. 

It  is  advisable  to  add  some  bromide  to  the 
developer  at  the  very  beginning  of  the  opera- 
tion, although  it  may  be  left  out  with  certain 
brands  of  plates.  Added  in  small  quantities 
this  restrainer  exerts  no  prejudicial  action  on 
the  details  of  the  shadows,  but  helps  to  keep 
the  cliche  clear,  especially  if  the  plate  has 
been  fully  exposed. 

Sodium  sulphite  has  a  marked  influence 
on  the  development  with  hydroquinone — the 
greater  the  dose  the  stronger  the  contrasts  and 
■vice  versa. 

By  diminishing  the  proportion  of  hydro- 
quinone less  density  is  obtained,  also  by  using 


148  THE  PHO  TO  GRA  PHIC  IMA  GE, 


large  doses  of  the  alkalies,  but  then  with  the 
usual  results. 

In  case  of  a  short  exposure-time  bordering 
to  under  exposure,  the  development  with 
hydroquinone  can  be  lengthened  more  than 
with  the  other  reagents,  which  is  a  great  boon 
to  obtain  what  can  be  had  of  the  delicate 
details  in  the  great  shadows.  The  developing 
solutions  should  be  diluted. 

To  develop  prepare — 

A.  Sodium  sulphite,  cryst.   .     .  50.  parts, 
Hydroquinone,  powdered       .  10.  ** 

Oitric  acid   3.  '< 

Potassium  bromide    .      .      .  0.5  part, 

Water   480.  parts. 

Heat  the  water  to  about  65°  C,  then  add  the  sulphite 
and  the  hydroquinone.  When  dissolved  let  cool  and  add 
ttie  other  chemicals. 

B.  Sodium  hydrate  .      .      .      .     10.  parts. 
Water   480. 

C.  Solution  of  potassium  bromide  1 : 10. 

For  normal  exposure, — Take  2  volumes  of 
1  volume  of  B,  dilute  with  1  volume  of  water; 
then,  according  as  the  image  comes  out,  add 
gradually  1  volume  of  B, 


DEVELOPMJlNT  with  HY'DROqUINONE.  149 


For  short  exposure. — Mix  equal  volumes  of  A 
and  B  ;  then,  according  to  circumstances,  add 
more  of  B  or  dilute. 

For  instantaneous  exposure. — Take  2  volumes 
of  B  and  1  volume  of  A  ;  then,  add  gradually 
more  of  A,  or  dilute. 

For  tentative  development. — Immerse  in  A^ 
diluted  with  1  volume  of  water  ;  then  proceed 
bj  adding  small  doses  of  a  sodium  hydrate 
solution  at  1:4,  or  operate  in  the  opposite 
manner,  according  to  the  exposure,  &c. 

The  above  method  of  compounding  the 
developing  solutions  is,  we  think,  more  rational 
than  that  which  consists  to  mix  a  new  solution 
with  an  old  one  in  proportions  varying  with 
the  exposure-times,  &c. 

The  method  referred  to  is  as  follows : 
A  ready-made    solution    is    prepared  as 
follows  : 

Sodium  sulphite  .     .     .     30.  parts, 
Hydroquinone     ...       5.  " 
Sodium  carbonate     .      .     70.  " 
Potassium  bromide   .     .      0.5  part, 
Water    ,     .     ,     ,     ,480.  part§. 


150  THE  PHOTOGRAPHIC  IMA  GE. 


This  constitutes  an  energetic  developer.  It 
can  only  be  employed  to  develop  plates 
exposed  by  the  drop  shutter  at  great  speed. 

By  use  it  undergoes  the  usual  changes.  It 
becomes  colored  and  liable  to  produce  a  yellow 
fog  difficult  to  remove ;  it  acts  more  and  more 
slowly  partly  from  the  oxidation  of  the  hydro- 
quinone,  partly  from  the  increasing  proportion 
of  potassium  bromide,  and  therefore  produces 
stronger  contrasts. 

To  counteract  the  too  energetic  action  of  the 
new  (stock)  solution,  one  advises  to  mix  it  with 
a  certain  quantity  of  the  old  developer  which, 
as  it  is  seen,  acts  as  a  restrainer.  For  example  t 

For  normal  exposures  one  uses,  say,  3  parts 
of  stock  solution  and  1  part  of  the  old. 

For  over  exposure  the  stock  and  old  solu- 
tions are  mixed  by  about  equal  volumes. 

For  short  exposure  the  proportion  of  the 
stock  solution  should  be  in  great  excess,  &c. 

Hence,  the  method  consists  to  regulate  the 
development  by  a  judicious  use  of  the  stock 
solution,  which  leads  to  produce  softness, 
mixed  with  the  old  restraining  developer. 


DEVELOPMENT  WITH  HYDRO QUIN ONE.  151 


Now,  the  reader,  by  comparing  this  method, 
with  the  simple  and  effective  manner  of  con- 
ducting the  development  with  pyrogallol,  will 
certainly  conclude  that  it  presents  no  advant- 
age but,  on  the  contrary,  leaves  one  in  doubt 
about  the  probable  action  of  the  mixture,  since 
the  old  solution  is  always  undergoing  altera- 
tions. 

The  following  is  a  developer  for  line-works  ; 

A.  Hydroquinone  ....  8  parts. 
Sodium  sulphite  cryst.       .  40 
Potassium  bromide      .      .  2  *' 
Water   480  " 

B.  Potassium  hydrate       .     6  to  8  parts. 
Water   480  " 

By  equal  volumes.    Mix  B  by  half  doseP 

After  development  the  plate  is  rinsed  under 
the  tap ;  then  immersed  for  two  minutes  into  a 
solution  of  tartaric  acid  at  three  per  cent  of 
water,  and  then  well  washed  and  fixed. 

The  acid  treatment  before  fixing  has  for  its 
object  to  effectually  prevent  yellow  fog. 

Berkeley's  fixing  bath  is  recommended  in 
this  and  the  eikonogen  developing  proceos. 


CHAPTEE  IX. 


The  Development  with  Eikonogen. 


The  reductive  action  of  eikonogen  is  rapid, 
unlike  that  of  pyrogallol  and  of  hydroquinone, 
similar  to  that  of  ferrous  sulphate  in  the  wet 
collodion  process,  developing  the  latent  image 
in  a  minute,  at  first  without  intensity  and 
giving  thereof  to  the  inexperienced  the  impres- 
sion that  the  plate  has  been  over  exposed. 

As  a  consequence,  eikonogen  has  a  tendency 
to  produce  very  soft  pictures  bordering  to 
flatness,  that  is,  pictures  without  sufficient 
contrasts. 

This  is  not,  however,  so  objectionable  as  it 
has  been  said.  We  think  it  is  even  advanta- 
geous, for  the  great  desideratum  in  most  cases 
is  to  obtain  the  details,  then  the  intensity. 


DEVELOPMENT  WITH  EIKONOGEN.  15^ 


To  prevent  the  tendency  to  flatness,  a  devel- 
oper strong  in  eikonogen  witli  a  good  percent- 
age of  alkali  and  restrained  as  soon  as  the 
image  is  wholly  visible,  should  be  employed. 
In  fact,  the  restrainer,  KBr,  is  generally 
useful  to  avoid  fogging,  especially  with  very 
rapid  plates. 

To  obtain  better  details  when  the  exposure- 
time  is  short,  some  authors  recommend  tr» 
immerse  the  plate  for  a  minute  in  the  following 
bath  before  developing,  then  to  proceed  with- 
out washing  the  film : 

Sodium  thiosulphate    •     .     •       1  part, 
Water   2000  parts: 

When  dissolved  add— 

Mercuric  chloride  sol.,  1;25,  .  5  to  10  parts. 

We  discard  this  preliminary  treatment. 

Eikonogen  is  a  very  good  developer  for  drop 
shutter  exposures. 

As  previously  said,  it  develops  the  whole 
picture  at  once,  so  to  say,  bringing  out  the 
details  in  the  shadows  rapidly  and  before  the 
lights  get  much  intensity  and,  indeed,  that  is  a 


154  THE  PHOTOGRAPHIC  IMAGE. 


great  quality ;  but,  then,  it  intensifies  slowly 
in  comparison  to  the  starting  action.  To 
intensify  quickly  and  to  obtain  brilliancy  the 
writer  has  recourse  to  pyrogallol  which,  when 
all  the  details  are  well  defined  and  only  then, 
is  added  by  small  quantities  to  the  developer; 
or  the  plate  may  be  treated  by  a  separate 
pyrogallol  developer  compounded  to  produce 
opacity. 

The  drawbacks  of  eikonogen  are  its  liability 
to  produce  fog^  and  its  exceedingly  rapid 
action  in  cases  of  unexpected  over  exposure- 
timos.  It  is  true  that  the  action  can  be 
checked  by  dilution,  adding  potassium  bromide 
or  neutralizing  part  of  the  alkali  with  citric 
acid,  but  then  the  results  are  seldom  as  good  as 
when  the  image  is  developed  with  pyrogallol. 

Yellow  fog  occurs  with  eikonogen  by  using 
large  doses  of  alkalies  without  the  correspond- 

*  When  the  exposure-time  is  short  the  reagent,  finding 
a  weak  impression  to  worli  upon,  is  liable  to  extend  its 
action — especially  when  the  development  is  slow— on  the 
parts  not  acted  on  by  light  and  thus  produce  fogging. 
Therefore  we  advise  for  instantaneous  (short)  exposure- 
times  a  very  energetic  eilionogen  developer  containing 
a  small  dose  of  potassium  bromide.  This  observation 
also  applies  to  any  developer. 


DEVELOPMENT  WITH  EIKONO GEN.  155 


Lag  percentage  of  sodium  sulphite,  or  by  long 
development,  or  by  employing  an  oxidized 
developer.  The  fog  is  sometimes  dichroic — 
green  by  reflection,  rose  or  pink  by  transpa- 
rency— and  results  from  the  same  cause  which 
produces  it  with  pyrogallol  and  hydroquinone  : 
the  dying  of  the  gelatine  film.  The  remedies 
are,  consequently,  the  treatment  with  an  acid 
clearing-solution  without  alum  before  fixing, 
and  fixing  in  the  thiosulphate — acid  sulphite 
bath.  The  following  clearing  solution  may  be 
used: 

Sodium  sulphite  .     .     .25  parts. 
Sulphuric  acid    .      .      .     5  " 
Water    ....       100  « 

The  color  of  the  cliches  developed  by  the 
reagent  in  question  is  a  grey-black  favorable 
for  rapid  printing,  but  requiring  to  push  the 
development  a  little  more  than  with  pyrogallol. 

To  develop,  prepare — 

A.   Sodium  sulphite,  cryst.     .      .      30  parts. 
Eikonogen,  cryst.  and  powdered,    IG  " 

Citric  acid  3  " 

Potassium  bromide  ...  2  " 
Water      ......     480  « 


156 


THE  PHOTOGRAPHIC  IMAGE, 


Eikonogen  is  slowly  soluble  in  cold  water. 
It  should  be  dissolved  in  water  heated  to  35°~ 
38°  C,  and  after  sodium  sulphite, 

B.    Sodium  sulphite,  cryst.     .     .     100  parts. 
Potassium  carbonate,  pure     .     120  " 
Water  480  « 

For  normal  exposure-time,  mix — 

A    ...    4,  volumes, 
B   .     .     .     1  volume. 
Water  .     .    3  volumes. 

For  over  exposure-time  mix,  in  the  same  pro- 
portions, and  restrain. 


For  short  exposure- 
ium  speed),  mix — 

A   .     ,  , 

Water  . 


(drop  shutter  at  med- 

3  volumes, 
1  volume. 
1 


time 


For  very  short  exposure-time  (drop  shutter  at 
rapid  speed),  mix — 

A   ...    3  volumes, 
B  ,     ,     .1  volume. 


DEVELOPMENT  WITH  EIKONOGEN.  157 


For  instantaneous  exposures,  prepare — 

4.1.    Sodium  metabisulphite      .     .      5.  parts. 
Eikongen,  cryst.  and  powd.      .  6. 
Water  150. 

B^.    Sodium  hydrate     ....       5.  parts, 
Potassium  bromide      .      .      .  0.25 

Water  30.  parts. 

Mix. 

This  constitutes  an  exceedingly  energetic 
developer.  •  It  may  be  diluted  with  1,  3^  5, 
volumes  of  water  according  to  the  exposure- 
time,  <fec.  To  obtain  contrasts,  add  bromide ; 
to  obtain  vigor  when  the  details  are  out,  have 
recourse  to  pyrogallol. 

The  developing  solutions  can  be  employed 
to  develop  several  images,  yielding,  then,  more 
intensity,  for  the  reasons  before  explained. 
They  are  consequently  good  for  developing 
plates  over  exposed,  to  obtain  contrasts,  &c. 
For  sh  ort  exposure-times  new  solutions  are,  as 
usual,  recommended. 

To  accelerate  the  intensification  and  obtain 
more  brilliancy,  &c.,  the  following  pyrogallol 
solution  can  be  added  to  the  eikonogen  devel- 
oper as  it  has  been  directed  : 


156  THE  PHOTOGRAPHIC  IMAGE. 


Sodium  bisulphite 

Pyrogallol 

Water 


1  part, 

2  parts. 

3  '« 


The  writer  here  states  once  more  that  the 
above  proportions,  good  in  ordinary  circum- 
stances, should  be  altered,  as  well  as  all 
others,  to  meet  certain  cases.  The  rules  laid 
down  for  developing  with  pyrogallol  stand 
necessarily  good,  no  matter  what  is  the  reagent 
employed. 

By  experimenting,  the  reader  will  soon 
ascertain  by  himself  that  eikonogen  and  hydro- 
quinone  do  not  permit  one  to  modify  the 
development  as  readily  and  effectively  as  does 
pyrogallol  which,  of  all  the  reagents  employed 
or  proposed  for  use  to  the  present  day,  pos- 
sesses the  greatest  elasticity  of  action ;  and, 
by  referring  to  the  generalities  on  the  behavior 
of  each  of  them,  he  will  be  able  to  apply  their 
special  properties  to  the  best  advantage  with- 
out the  necessity  of  our  further  consideration 
on  this  subject. 


CHAPTER  X. 


Development  with  Pebrous  Oxalate. 


Four  stock  solutions  are  employed  to  com- 
pound the  developers,  viz : 

A.  Neutral  potassium  oxalate,  .  200  parts, 
Potassium  bromide.  .  .  1  part, 
Water   600  parts. 

If  this  solution  shows  an  alkaline  reaction  to 
test  paper  it  should  be  slightly  acidified  with 
oxalic  acid. 

• 

B.  Ferrous  sulphate  ...    60  parts. 
Sugar,  white      .  c     .     •    15  '* 
Tartaric  acid     .  .      .     .     2  •* 
Water,  ordinary  .     .     .  200  " 

The  solution  keeps  well  owing  to  the  organic 
matters  which  by  being  oxidized  through  the 
ferric  salt  as  it  forms  reduce  it  to  i'orrosum. 

Should  it  become  turbid  a  small  quantity  of 
tartaric  acid  must  be  added  and  the  solution 
exposed  to  light. 


160 


THE  PHOTOGRAPHIC  IMAGE. 


C.  Potassium  bromide  .     .     .     o     .  1  part, 
Water   10  parts, 

D.  Sodium  thiosulphate,  (hyposulphite)  1  part, 
Water   1000  parts. 

The  solution  D  is  the  accelerator  ;  G  is  the 
restrainer. 

The  effect  of  D  is  almost  instantaneous  ;  the 
details,  which  otherwise  it  would  be  impossible 
to  force  out  when  the  exposure-time  is  short, 
appears  simultaneously  with  a  slight  veil 
covering  the  picture.  If  added  in  too  great  a 
quantity  it  produces  a  dense  fog  and  the 
picture  is  spoiled  past  remedy.  One  per  cent 
of  the  developing  solution  is  the  maximum 
dose. 

A  saturated  solution  of  potassic  ferrous 
oxalate  is  prepared  by  gradually  adding  1  part 
of  ^  to  3  parts  of  Ay  not  the  reverse.  It 
constitutes  the  most  energetic  developer  which 
can  be  made  with  this  salt.  It  should  be 
prepared  just  before  use,  its  energy  diminish- 
ing sensibly  from  oxidation  in  contact  with  the 
air  and  during  the  development  by  the  acces- 
sion of  potassium  bromide. 

Under  the  action  of  this  compound  the 


DEVELOPMENT  WITH  FERROUS  OXALATE.  161 


image,  when  the  exposure  is  right,  appears 
within  15  or  20  seconds,  The  high  lights  first 
make  their  appearance  and  then  the  half  tints. 

If  the  plate  is  over  exposed,  the  image 
flashes  out  soon  after  its  immersion  in  the 
developer  and  the  half  tints  come  out  almost 
simultaneously  with  the  high  lights.  The 
action  should  then  be  restrained  at  once  and 
the  developer  diluted. 

On  the  other  hand,  if  the  high  lights  do  not 
appear  within  30  seconds,  or  if  the  half  tints 
hang  back,  which  indicates  a  short  exposure- 
time,  D  is  added,  but  only  when  the  image 
shows  a  commencement  of  development,  unless 
the  operator  knows  that  the  exposure-time  is 
very  short,  when  the  plate  may  be  immersed 
for  an  instant  in  a  very  diluted  solution  of  D 
(5  to  10  per  1000)  and  then,  without  washing, 
placed  in  the  developing  solution.* 

*  Audra. 

By  compounding  the  accelerator  with  potassium 
bromide  as  in  the  following  formula,  lager  doses  can 
be  added  either  to  the  developing  solution  or  to  the 
preliminary^  bath,  say,  from  3  to  4  per  100.  The  cliche  is 
less  liable  to  fog  on  account  of  the  small  quantity  of 
bromide,  therefore  more  clear  and  brilliant  images  are 
obtained : 

Sodium  thiosulphate     .     .        1  part, 
Potassium  bromide      .     .        2  parts. 
Water  480 


162  THE  PHOTOGRAPHIC  IMAGE, 


As  usual  with  the  other  reagents,  it  is 
advisable  to  commence  the  development  with 
little  iron  and  to  gradually  increase  the  dose, 
but  without  exceeding  the  proportion  of  1  5  to 
8  Ay  and  observing  that  a  solution  weak  in 
ferrous  oxalate  tends  to  produce  more  contrasts. 

The  following  formulas  are  given  as  exam- 
ples, no  account  being  taken  of  the  lighting : 

For  normal  exposure,  commence  with  12  A 
and  3  B.    (Maximum  of  B,  4) 

For  over  exposure,  use  in  the  same  proportion 
as  for  normal  exposure  and  restrain. 

For  slightly  short  exposure,  use  15  A  and  4:  B ; 
then  add  D  to  obtain  details.    (Maximum  oJ 

5.) 

For  short  exposure,  3  A  and  IB;  then  add  Z>. 
All  these  developers  should  have  an  acid 
reaction,  else  they  produce  fogging. 

Observe  that  in  this  as  in  the  other  develop- 
ing processes  heat  accelerates  the  action  and 
tends  to  force  out  the  details  which  hang  back, 
and  that  by  employing  the  same  solution  to 
develop  2,  3,  4  cliches,  the  development  pro-» 
ceeds  more  and  more  slowly  and  the  contrasts 
increase. 


DEVELOPMENT  WITH  FERROUS  OXALATE,  163 


To  reduce  to  ferrosum  tlie  ferric  oxalaw 
formed  during  the  development  whicli,  more 
than  the  bromide,  impairs  the  reductive  power 
of  the  reagent,  add  a  little  tartaric  acid  to  the 
solution  and  expose  it  to  sunshine  for  a  few 
hours,  until  the  dark  red  color  of  the  liquid 
turns  to  a  ruby  tint.  The  developer  is  then 
ready  for  use.  As  the  bromide  resulting  from 
the  reduction  of  the  silver  salt  still  restrains 
the  energy  of  the  regenerated  ferrous  oxalate, 
it  is  useful  in  order  to  obtain  soft  cliches  to 
counteract  this  action  by  adding  a  small 
quantity  of  the  accelerator  D.  This  will  be 
practically  effective  so  long  as  KBr  is  not  in 
too  great  a  proportion. 

In  order  to  prevent  the  oxidation  of  a  ready 
made  developer  it  has  been  advised  to  com- 
pound it  with  some  sodium  sulphite,  that  is,  a 
permanent  deoxidizer,  thus : 

E.  Solution  A       ....    100  parts. 
Sodium  sulphite  cryst.       .       6  *' 

F.  Solution  B      ....     33  parts, 
Tartaric  acid   ....      1  part. 

Mix. 

When  developed,  the  plate  is  washed,  cleared 


164  THE  PHOTOGRAPHIC  IMAGE, 


in  a  solution  of  citric  add,  washed  again,  then 
fixed,  &G. 

The  color  of  the  cliches  developed  with 
ferrous  oxalate  is  a  grey  or  bluish-blacli — very 
favorable  for  rapid   printing   and  transpa 
rencies. 

The  writer  of  this  work  thinks  that  ferrous 
sulphate  is  the  best  developer  in  microphotog- 
raphy  on  account  of  the  fineness  of  the  silver 
deposit  and  the  freedom  from  fogs  and  stains. 

Pyrogallol  cannot  be  employed  with  ferrous 
oxalate,  a  black  precipitate  is  formed. 


CHAPTEK  XI. 


§  1.  Development  with  Pyeocatechin. 


Pyrocatechin  was  introduced  for  the  devel- 
opment of  collodion  cliches  by  Mr.  E.  Wagner, 
in  1859.  Lately  Dr.  J.  M.  Eder  applied  it  to 
the  gelatine  process.  The  formula  published 
by  the  learned  doctor  is  the  following : 


A.  Pyrocatechin 
Sodium  sulphite 
Water  . 


B,   Potassium  carbonate 
Water  .... 


1  part, 
4  parts. 
50  «< 

4  parts. 
40  " 


Mix  1  of  J.  to  2  of  B. 


This  developer  acts  more  rapidly  than 
hydroquinone,  permits  to  lengthen  the  devel- 
opment, and  yields,  clear  cliches  free  from  fog 
and  having  fair  printing  qualities. 

It  is  little  employed,  and  in  our  opinion 
presents  no  serious  advantages  over  pyrogallol. 


166  THE  PHOTOGRAPHIC  IMAGE. 


§  2.  Development  with  Hydroxylamine. 


A.   Chlorhydrate  (chloride)  of 
hydroxylamine  . 
Alcohol  .... 


30  parts. 
480  '* 


B.   Caustic  potash  . 
Water  . 


60  parts. 
480  " 


C.   Potassium  bromide 
Water  . 


20  parts. 
480  •» 


"  To  develope,  take  30  parts  of  A,  40  parts 
of  Bf  and  10  parts  of  C  diluted  with  480  parts 
of  water ....  the  development  proceeds  rapidly 
and  is  completed  in  about  five  minutes. 

"  The  advantages  claimed  are  :  wide  latitude 
of  exposure,  non  deterioration  of  the  solution 
from  external  sources,*  and  absolute  freedom 
from  fog  or  stains — a  gain  that  cannot  be  too 
strongly  accented. 

"Against  these  important  advantages  I 
should  state  that  there  is  a  minor  objection, 
and  that  is  the  liability  to  cause  recticulation 
from  the  softening  of  the  film  by  the  caustic 

*  Hydroxylamine  does  not  absorb  oxygen  from  the 
air  in  presence  of  alkalies. 


DEVELOPMENT  WITH  PARAMIDOPHENOL,  1G7 


alkali  and  tho  evolution  of  nitrous  oxide  from 
the  decomposition  of  the  hydroxylamine.""^ 

The  tendency  to  frilling  which  Mr.  Spiller 
speaks  of  is  not  entirely  pe-culiar  to  the 
process ;  with  certain  brands  of  plates  it  occurs, 
whatever  be  the  reagent,  if  it  is  compounded 
with  large  doses  of  strong  alkalies.  However, 
in  this  process  the  defect  is  not  always  avoided 
even  by  adding  a  little  alcohol  to  the  developing 
solution  or  using  less  alkali,  for  it  is  mostly  due 
to  the  nitrous  oxide  evolved  during  the  decom- 
position of  hydroxylamine. 

This  process  is  little  employed,  requiring  a 
longer  exposure-time  than  pyrogallol  to  obtain 
the  same  intensity,  and  being  prone  to  produce 
blistering  as  previously  stated. 

S  3.  Development  with  Paramidophenol. 


"  Paramidophenol,'*  says  Messrs.  Auguste 
and  Louis  Lumiere,  who  applied  the  reductive 
properties  of  this  compound  to  the  develop- 


*  Arnold  Spiller. 


168  THE  PHOTOGRAPHIC  IMAGE. 


ment  of  tlie  photographic  image,^  "in  pres- 
ence of  a  base  or  of  an  alkaline  carbonate 
possesses  remarkable  reductive  properties 
■which  render  it  valuable  as  a  developer.'* 

The  reduction  of  the  silver  bromide  is 
effected  in  the  ordinary  manner. 

"Water  is  decomposed ;  the  oxygen  is 
absorbed  by  Paramidophenol  with  formation 
of  quinonimide  (or  quinone)  while  the  hydro- 
gen reduces  the  silver  bromide  by  uniting  to 
the  haloid. 

Paramidophenol  is  the  product  of  the  action 
of  tin  and  hydrochloric  acid  on  paranitro- 
phenol.  It  crystallizes  in  plates  which  melt 
at  184^  C.  in  being  decomposed.  At  0^  C.  it 
dissolves  in  90  parts  of  water  and  in  22  parts 
of  absolute  alcohol.    Formula : 


The  solubility  of  paradiphenol  is  not  much 
increased  by  the  temperature. 

The  aqueous  solution  oxidizes  in  the  air 
assuming  a  violet-red  tinge  especially  in  pres- 
ence of  the  alkaline  bases  with  which  paradi- 

*  Bull.  Assoc.  Beige  Phot.,  Vol.  XVIII,  p.  435  et  aeq. 


DEVELOPMENT  WITH  PARAMIDOPHENOL.  169 


plienol  combinesi  in  forming  salts  possessing 
powerful  reducing  properties.  (Andressen,) 

The  following  formulas  answer  well  for  the 
development  of  gelatino-bromide  of  silver 
plates : 


Paramidophenol 

12  parts. 

Sodium  sulphite 

.  200 

Sodium  carbonate  . 

.  100 

« 

Water  .... 

.  1000 

(( 

Paramidophenol 

12  parts. 

Sodium  sulphite 

.  200 

(( 

Lithium  carbonate  . 

.  12 

<( 

"Water  .... 

1000 

(( 

The  first  formula  forms  a  very  energetic 
developer  which  answers  for  plates  instanta- 
neously exposed. 

As  a  developer  paramidophenol  presents  the 
inconvenience  of  not  being  sufficiently  soluble, 
so  that  it  is  not  possible  to  make  in  the  con- 
stitution of  the  developer  as  many  modifica- 
tions r-s  those  possible  with  a  very  soluble 
body  SI, eh  as  pyrogallol. 

Hydroquinone  and  eikonogen  also  present 
this  inconvenience  to  the  same  degree,  but 
paramidophenol  possesses  over  them,  hydro- 
quinone especially,  the  adTa,iitage  of  never 
coloring  the  gelatine. 


170 


THE  PHOTOGRAPHIC  IMAGE. 


The  solution  k'^'^ps  for  a  long  time,  even  in 
uncorked  vials,  and  the  cliches  developed  by 
an  old  bath  are  free  from  that  yellow  fog  often 
occuring  when  using  other  developers. 

The  action  of  the  paramidophenol  developer 
is,  by  use,  very  slowly  exhausted,  and  this  to 
such  a  point  that  in  100  grams  of  solution  one 
can  develop  6  or  7  plates  13x18  c.  m.  without 
any  appreciable  difference  between  the  first 
and  the  last.* 

Lately  Messrs.  Lumiere  have  published  the 
following  formula  as  working  better  than  those 
they  had  first  given : 

Water   800  parts. 

Potassium  carbonate    ,  40  ** 

Sodium  sulphite     .     .  100  '* 

Paramidophenol     .     ,  8  " 

Andressen  compounds  the  developer  as 
follows : 

Hydrochloride  of  paramidophenol      .        5  parts. 

Sodium  sulphite  cryst  50  ** 

Potassium  hydrate  25  ** 

Water   1000  *• 


*  Here,  especially,  we  do  not  agree  with  the  inventors. 
The  alkaline  bromide,  the  propci  ulon  of  which  increases 
with  every  plate  developed  exerts  its  action  with  the 
usual  results,  as  also  the  various  doses  of  allcalL 


PAET  III. 


The  Development  in  the  Negative  and 
osiTivE  Collodion  Processes,  and 
IN  THE  Silver  Bromide 
Printing  Processes. 


CHAPTER  I 


The  Development  in  the  Collodion 
Process. 


In  the  collodion  wet  process  the  image  is 
developed  by  a  solution  of  ferrous  sulphate 
acidified  by  acetic  acid  :  the  silver  nitrate  in 
excess  on  the  photo  film  being  reduced  by  the 
salt  of  iron  precipitates  with  adherence  upon 
the  impressed  parts  and  forms  the  image. 
During  the  action  the  silver  film  is  not  altered, 
for  if  the  image  be  dissolved  by  nitric  acid, 
or,  as  shown  by  Mr.  Carey  Lea*,  by  mercuric 
nitrate,  it  is  possible  to  take  upon  it  another 
impression  by  the  same  means.  It  is  well 
known  that  ferrous  sulphate  does  not  act  on 
the  silver  haloids. 

It  is,  indeed,  a  very  remarkable  phenomenon 
that  the  change,  generated  by  the  dynamic 


*  PhiL  Photographer,  1865  and  1886. 


1 74  THE  PHO  TO  GRA  PHIC  IMA  GE. 


action  of  light  in  tlie  molecular  state  of  tlie 
silver  haloids  previously  to  the  dissociation  of 
the  elements,  which  causes  them  to  be  reduced 
by  a  chemical  developer,*  also  exert  an 
attractive  action  on  metallic  silver  in  a  state  of 
nascent  reduction,  and  that,  proportionally  to 
the  degree  of  insolation,  so  that  the  silver 
atoms  are  attracted  with  more  or  less  energy 
and  consequently  precipitate  in  more  or  less 
quantities,  thus  forming  an  image  in  gradation 
of  tints;  the  reader  remembers  that  by  the 
alkaline  method  of  development  the  image  is 
formed  by  the  silver  reduced  from  the  photo 
film  itself. 

The  reduction  of  silver  nitrate  by  ferrous 
sulphate  is  rapid.  Almost  as  soon  as  the 
developing  solution  is  flowed  on  the  impressed 
photo  film  the  image  appears  and  is  wholly 
developed  in  less  than  one  minute.  It  is  not, 
therefore,  possible  of  regulating  the  develop- 

*  This  term  is  applied  to  the  developers  which  reduce 
the  impressed  silver  haloids,  alkaline  pyrogallol,  ferrous 
oxalate,  hydroquinone,  etc.,  to  distinguish  them  from  the 
acid  or  physical  developers,  ferrous  sulphate,  ferrous 
nitrate,  etc.,  which  do  not  act  on  these  salts  and  cause 
the  development  of  the  image  by  reducing  the  silver 
nitrate  as  here  explained. 


DEVELOPMENT  IN  COLLODION  PROCESS.  175 


ment  as  with  a  chemical  developer  whose 
action  is  gradual  and  slow :  other  means 
should  be  resorted  to  in  order  to  obtain  either 
softness  or  vigor. 

These  means  are  :  the  constitution  of  the 
collodion,  the  state  of  the  silver  bath,  the 
iBxposure-time,  the  more  or  less  energy  of  the 
developing  solution,  the  redevelopment  and 
intensification. 

This  work  having  for  its  especial  object  to 
guide  the  student  in  the  operations  of  the 
development,  we  shall  not  describe  how  to 
make  a  suitable  collodion  to  obtain  soft  or 
brilliant  images,  nor  shall  we  enter  into  the 
description  of  the  causes-  which  impair  the 
silver  bath,  of  the  manner  of  restoring  it  to 
working  order,  nor  give  a  detailed  list  of  the 
failures  occuring  in  the  process.  For  instruc- 
tions on  these  matters  we  refer  the  reader  to 
treatises  on  general  photography.  However, 
we  will  state,  incidentally,  that  to  obtain 
intensity  the  collodion  should  be  thick  and 
well  bromo-iodized,  and  the  same  diluted  for 
soft  pictures — portraits,  for  example. 

In  the  wet  collodion  process,  the  exposure- 


176  THE  PHOTOGRAPHIC  IMAGE. 


time  is  one  of  the  most  important  factors, 
since  the  development  is  almost  purely 
mechanical.  When  the  time  is  short  no 
details  are  obtained  in  the  deep  shadows,  if 
the  plate  is  over  exposed,  the  image  is  grey, 
too  uniform  and  liable  to  fog.  However,  it 
is  advantageous  when  the  subject  is  in  half- 
tones to  somewhat  over  expose,  because  by 
reducing  or  intensifying — to  which  we  are 
often  obliged  to  resort  in  this  process  to  obtain 
a  good  printing  general  intensity — more  con- 
trasts are  always  the  result. 

Compared  to  gelatine,  the  exposure  should 
be  about  ten  times  longer  than  the  plates  of 
ordinary  rapidity,  say  20  Warnerke. 

The  developer  for  the  wet  collodion  process 
is  compounded  in  four  different  manners,  viz : 


1.    Normal  Developer. 


Ferrous  sulphate 
Acetic  acid  No.  8 
Sulphuric  acid  . 
Water  . 


40  " 
3  " 
480  " 


30  parts. 


This  is  the  standard  developer, 
and  keeps  well  owing  to  the 


It  is  strong 
presence  of 


DEVELOPMENT  IN  COLLODION  PROCESS.  177 


sulphuric  acid  preventing  oxidation.  A  little 
alcohol  should  be  added  to  it  when  it  does  not 
flow  well. 

2.    Energetic  Developer. 
Ferrous  sulphate      ...    40  parts. 


Acetic  acid  No.  8 
Glucose 

Copper  acetate  . 
Water  . 


30 
20 

480 


This  developer  should  be  prepared  several 
hours  beforehand  and  heated  to  25°  C.  for 
use.  It  develops  rapidly,  yielding  soft  nega- 
tives full  of  details.  The  silver  bath  should 
be  acidified  with  acetic  acid,  C.  P. 

If,  instead  of  acetate,  1^  parts  of  sodium 
formate  and  3  parts  of  formic  acid  are  added, 
the  most  powerful  developer  employed  in  the 
wet  collodion  process  is  obtained. 

3.    Weak  Developer. 
Ferrous  sulphate     .       15  to  20  parts. 
Acetic  acid  No.  8      .  ,    .      .    45  '* 
Sulphuric  acid   .     .     .     .     2  " 
Water    .      .      .      .      .      .  480  " 

4.    Developer  for  Line-worlcs. 
(Engravings,  Etc.) 
Ferrous  sulphate      .      .     c    25  parts. 
Tartaric  acid      .     •      .    4  to  5  ** 
Water    ......  480  '* 

Alcohol  qitant.  suff. 


178 


THE  PHOTOGRAPHIC  IMAGE. 


This  developer  kept  in  the  light  does  not 
oxidize.  It  acts  slowly.  The  image  appears 
in  from  20  to  30  seconds  and  then  gradually 
intensifies.  Generally  the  blacks  are  very 
intense  and  the  whites  (clear  glass)  free  from 
silver  deposits,  which  is  of  great  importance 
when  the  cliche  should  be  intensified  and  used 
in  photo-engraving.* 

It  must  be  observed  that  a  weak  developer, 
that  is,  working  slowly,  tends  to  give  contrasts, 
while  a  strong  developer  such  as  1  and  2 
promotes  softness  in  securing  details.  Here 
again  the  rule  before  laid  down  holds  good : 
to  obtain  gradation,  the  details  should  be 
brought  out  before  the  high  lights  get  inten- 
sified. 

*  We  advise  the  reader  to  use  with  this  developer  a 
collodion  compounded  with  zinc  iodide  and  bromide, 
thus: 

Sodium  iodide    ...     5  parts, 
Zinc  iodide  ....     1  part, 
Zinc  bromide     .     .     .     1  " 
Collodion,  plain      .     .  480  parts. 

The  plain  collodion  should  be  made  with  a  pyroxiline 
prepared  at  a  high  temperature  and  have  a  good  body. 
This  iodo-bromized  collodion  does  not  keep  well.  It  is 
best  to  have  the  iodides  and  the  bromide  in  separate 
solution  and  to  mix  by  quantities  sufficient  for  about  a 
week's  use. 

The  silver  bath  should  be  acidified  with  nitric  acid 
chemically  pure. 


DE  VEL  OPMEN  T  IN  COL  L  ODION  PR  0  CESS.  179 


develop,  tlie  plate  is  placed  on  a  stand 
held  in  the  left  hand  and  the  developer  flowed 
over  the  film  from  the  lower  edge  of  the  plate 
with  a  gentle  sweep  from  left  to  right  so  that 
the  liquid  runs  in  one  even  sheet  and  covers 
the  whole  film  at  once.  During  the  develop- 
ment the  liquid  should  be  kept  in  mo(;ion 
taking  care  that  every  part  of  the  film  be 
alternatively  washed. 

At  this  stage  of  the  operation  one  can  judge 
whether  the  exposure-time  is  right.  When  it 
is  short  the  image  appears  slowly  and  the 
details  in  the  shadow^s  refuse  to  come  out, 
whilst  in  the  case  of  excess  of  exposure  it 
flashes  out  instantly  in  all  its  parts  but  with- 
out sufficient  contrasts.  The  development  of 
well  exposed  plates,  although  quite  rapid, 
proceeds  gradually. 

The  action  of  the  developer  i's  exhausted  in 
a  minute  and  if  the  exposure-time  is  sufficient, 
the  development  does  not  require  more  than 
about  half  that  time  to  bring  out  the  faintest 
details  in  the  shadows;  then  the  film  should  be 
washed  under  the  tap  and  fixed. 

The  failures  from  the  development  arise  from 


180 


THE  PHOTOGRAPHIC  IMAGE. 


tlie  irregular  flooding  of  the  plate.  They 
appear  as  streaks  and  markings  which  are 
avoided  by  observing — 

1st.  Not  to  flow  the  developer  from  the 
lower  edge  of  the  plate  before  the  latter 
has  been  drained  on  blotting  paper,  for  the 
silver  solution  there  accumulated  during  the 
exposure-time  may  be  carried  irregularly  over 
the  film  and  form  streaks  of  intensity ; 

2nd  To  flow  the  developer  in  an  even 
stream,  so  that  it  does  not  divide  in  several 
rivulets,  because  the  silver  solution  pushed  on 
the  film  by  these  various  streams  accumulates 
at  their  point  of  junction  and  there  deter- 
minates markings  of  opacity 

3rd.  To  avoid  pouring  violently  the  devel- 
oper on  the  film.  In  this  case  hair  lines  are 
usually  formed,  radiating  from  the  place  the 
developer  has  been  poured  on. 

These  hair  lines  are  sometimes  also  pro- 
duced by  strong  developers,  that  is,  containing 
large  proportions  of  ferrous  sulphate.  This 
especially  happens  in  reproducing  subjects  on 
a  white  ground.    The  remedy  is  obvious. 

4th.  Lastly,  not  to  pour  the  developer 
steadily  on  one  spot,  as  the  silver  nitrate  being 


DEVELOPMENT  IN  COLLODION  PROCESS.  181 

tlius  washed  away,  the  negative  remains  there 
more  transparent  than  on  the  other  parts. 

The  cliches  are  intensified  either  by  Be- 
development ,  or  by  chemical  actions  similiar  to 
those  employed  in  the  gelatine  process  and 
classified  under  the  title  of  Intensi^cation. 

Ee-development  :  The  re-development  is 
especially  adapted  for  half  tone  subjects.  It 
is  done  in  the  dark  room  just  after  the  devel- 
opment proper,  in  order  to  preserve  the  most 
delicate  shades  and  details  which  may  be 
dissolved  by  the  fixing  agent,  potassium 
cyanide. 

As  the  name  indicates  it,  this  operation  is 
nothing  else  than  the  continuation  of  the 
development.  It  is  effected  by  treating  the 
cliche,  well  washed,  by  a  solution  of  pyrogallol 
to  which  is  added  a  small  quantity  of  a  silver 
nitrate  solution  : 


A.  Pyrogallol 
Citric  acid 


1  part. 

2  parts. 


Water 


.  480 


B,   Silver  nitrate 


.  15  parts. 
.  480 


Water 


182 


THE  PHOTOGRAPHIC  IMAGE 


It  should  be  observed  not  to  increase  tlie 
general  intensity  beyond- that  absolutely  neces- 
sary to  obtain  good  prints,  because  the  image 
does  not  preserve  the  same  relation  between 
the  high  lights,  the  half  lights,  etc.,  but 
increases  in  contrasts,  the  silver  being  depos- 
ited in  greater  quantities  on  the  parts  where 
there  is  already  a  denser  layer  of  metal.  It 
may  be  said  that  the  affinity  of  silver  in  the 
nascent  state  of  reduction  for  the  metal  form- 
ing the  image  is  in  the  ratio  of  the  mass 
deposited  during  the  development. 

It  sometimes  happens  that  by  re-developing 
after  fixing,  an  inverse  action  takes  place^  the 
negative  being  converted  into  a  positive.  This 
effect  which  commences  to  manifest  itself  by  a 
reddish  reduction  in  the  deep  shadows  and  at 
the  edges  of  the  cliche,  is  avoided  by  flowing 
the  plate  with  a  solution  of  iodine  or  of 
mercuric  iodide  in  sodium  iodide  and  washing 
before  applying  the  re-developing  mixture. 
The  solution  of  mercuric  iodide  must  be  weak 
and  allowed  to  act  for  two  or  three  seconds. 

A  stock  solution  of  potassic  mercuric  iodide 
may  be  prepared  by  adding  gradually  to  a 
solution  of  potassium  iodide,  4 : 100,  another 


DEVELOPMENT  IN  COLLODION  PROCESS.  183 


of  mercuric  chloride  (saturated)  until  the  red 
precipitate  forraed  does  no  more  dissolve. 

The  re-development  with  ferrous  sulphate 
recommended  by  some  authors  is  not  so 
effective  as  that  with  pyrogallol,  nor  so  great 
an  intensity  can  be  obtained.  But  it  some- 
times brings  out  details  not  fully  developed 
on  account  of  the  rapid  reduction  of  silver 
nitrate  by  ferrous  sulphate.  For  line  works 
it  is  objectionable,  for  the  lines  are  liable  to  be 
blocked  up  by  a  deposit  of  silver. 

This  developer  consists  of  a  solution  of  from 
8  to  10  parts  of  ferrous  sulphate  and  half  the 
quantity  of  citric  acid  in  480  parts  of  water,  to 
which,  for  use,  is  added  a  little  of  the  silver 
nitrate  solution  whose  formula  is  above  given. 

The  mixture  is  flowed  on  the  cliche  jast 
after  developing  and  washing. 

Intensification  :  In  the  collodion  process, 
either  wet  or  dry,  the  intensification  is  em- 
ployed for  cliches  in  lines,  not  for  those  in 
half  tones,  for  the  medical  action  is  rapid  and 
cannot  be  well  controlled. 

Many  processes  can  be  employed  to  intensify 
line  cliches.    We  will  describe  the  most  em- 


164  THE  PHO TOGRAPHIC  IMA GE. 


ployed — those  of  Prof.  Ad.  Martin,  of  Dr.  Eder 
Toth,  and  of  Wm.  Cambell. 

1st.  Professor  AdolpJi  Martins  process 
(1861), — When  the  image  is  fixed  t  and  well 
washed  it  is  treated  by  a  plain  solution  of 
bichloride  of  mercury  until  uniformly  whitened. 
It  is  then  carefully  washed  and  a  solution  of 
double  cyanide  of  silver  and  potassium  is 
poured  over.  This  solution  is  prepared  by 
adding  to  a  10  per  100  solution  of  potassium 
cyanide  a  saturated  solution  of  silver  nitrate 
until  the  precipitate  formed  is  no  more,  dis- 
solved by  agitation.  The  liquid  is  then  filtered 
and  a  very  small  excess  of  potassium  cyanide 
is  added.  Instead  of  silver  nitrate,  the  copper 
salt  can  be  used  ;  the  lesult  is  the  same. 

The  metal  precipitated  by  the  chemical 
action  is  black  and  increases  the  intensity  of 
the  negative. 

This  process  may  be  used  for  toning  diapos- 
itivtJis. 

Sodium  thiosulphate  (hyposulphite)  may  oe 

*  This  process  has  been  wrongly  attributed  to  Dr. 
Monclihoven  by  engUsh  authors.  Old  processes  are  often 
revived  without  giving  the  honor  of  the  invention  to 
whom  it  is  due. 

I  It  should  be  fixed  by  potassium  cyanide. 


DEVELOPMENT  IN  COLLODION  PROCESS.  185 


substituted  for  potassium  cyanide  and  the 
solution  prepared  in  the  same  manner,  but  not 
in  great  quantities — it  does  not  keep. 

The  cliche  should  not  be  fixed  after  tMs 
operation ;  it  suffices  to  wash  it  well. 

By  repeating  over  these  operations,  the 
negative  can  be  intensified  to  any  desired 
extent  without  risk  of  any  reduction  being 
formed  in  the  transparent  parts  if  they  are 
clear  from  reduced  silver. 

William  CamphelVs  process  (1876).*  For  line 
works — Into  a  saturated  solution  of  sulphate 
of  copper  pour  a  solution  of  bromide  of  potas- 
sium enough  to  turn  the  color  of  the  negative 
to  a  white.t  This  may  be  done  either  by 
pouring  off  and  on  several  times  the  solution, 
or  leaving  the  plate  in  a  dish  till  the  color 
changes  (bleaches) ;  the  stronger  the  bromide 
in  the  solution,  the  quicker  will  it  change.^ 

*  This  process  has  been  wrongly  attributed  to  Captain 
A.bney. 

t  The  following  solution  may  be  employed : 
Potassium  bromide  ...     3  parts. 
Cupric  sulphate  .      .      .      .     6  " 
Water  120  " 

I  Cuprous  and  argentic  bromide  are  formed.  (See 
.Either  on.) 


m  THE  PHOTOGRAPHIC  IMAGE. 


When  this  stage  is  obtained,  wash  the  plate 
and  pour  on  a  dilute  (2  : 100)  solution  of  silver 
nitrate  ;  the  film  will  now  become  denser,  and 
black.  If  not  dense  enough  repeat  the  opera- 
tion.* It  is  rarely  necissary  to  go  further; 
but  if  any  disappointment  is  experienced,  it  is 
a  sure  sign  of  derangement  in  the  (sensitizing 
silver)  bath — perhaps,  too  weak.f 

For  portraits  and  similar  works  it  is  not 

*  The  chemical  actions  are  represented  thus  : 
Cu2Br2+4  AgN03=2  Cu(N03)2-}-2  AgBr  +  Ag^. 

if  Whatever  be  the  intensifying  process  employed,  it  is 
necessary,  in  order  to  obtain  opacity,  that  the  image  be 
formed  by  a  certain  quality  of  metallic  silver,  that  is,  not 
too  weak,  since  the  result  of  the  chemical  action  depends 
Upon  th^  thickness  of  the  layer  of  this  metal.  In  the 
process  we  describe  the  changes  taking  place  by  treating 
the  cliche  with  cupric  bromide  are  as  follows ; 

2  CuBrg-f  Agj^^CUgBra  +2  AgBr. 
Hence  the  amount  of  cuprous  bromide  reacting  with 
silver  nitrate  to  obtain  intensity  is  proportionate  to  that 
of  the  metallic  silver  originally  forming  the  image.  If 
the  image  is  weak,  we  advise  the  operator  to  re-develop 
it  before  intensifying. 

It  is  always  very  important,  before  intensifying  cliches 
from  engravings,  etc.,  that  the  lines  be  clear,  that  is,  free 
from  any  deposit  of  silver ;  the  reason  is  obvious.  If  the 
lines  were  partly  blocked  up,  no  matter  how  little  the 
silver  deposit,  they  should  be  cleared  by  treating  the 
cliche  with  a  solution  of  iodine  in  potassium  cyanide 
(cyanide  of  iodine).  The  solution  should  be  diluted  and 
applied  with  care  for  it  rapidly  dissolves  the  metal. 


DEVELOPMENT  IN  COLLODION  PROCESS.  187 


necessary  to  carry  the  treatment  with  mercury 
to  the  white  stage,  simply  pouring  altern^ 
atively  the  solutions  and  washing  well  the 
plate,  till  the  required  intensity  is  sufficient. 

Dr,  Eder  and  TotJis  process  (1876). 

Ked  prussiate  of  potash   .    .     .    30  parts. 

Nitrate  of  lead  20  *' 

Distilled  water   488  «' 

Distilled  or  rain  water  should  be  employed. 
Any  water  containing  lime  will  cause  a  pre- 
cipitate all  over  the  negative. 

The  negative  is  dipped  into  this  bath  or 
it  may  be  flowed  over  it  as  soon  as  it  is 
fixed  and  well  washed.  During  the  action 
of  the  lead  bath  there  is  deposited  on  the 
silver  parts  of  the  picture  a  faint  yellowish- 
white  precipitate  which  makes  the  film  appear 
quite  white  and  possesses  an  extraordinary 
amount  of  intensity.  It  is  necessary  to  let 
the  negative  remain  in  the  bath  until  it  has 
assumed  the  same  amount  of  density  which 
you  require  in  the  end,  for  the  after  treatment 
with  ammonium  sulphide  is  rather  for  the 
purpose  of  rendering  the  reduction  permanent 
than  to  change  the  density. 


188  THE  PHO  TO  GRA  PHIC  IMA  G E. 


After  the  negatives  have  been  taken  out  the 
lead  bath  and  well  washed  with  distilled  or 
rain  water,  the  following  solution  is  applied : 

Ammonium  sulphide     ...     30  parts 
Water   480 

Immediately  upon  this  application,  the 
image  becomes  perfectly  black  and,  when  the 
reduction  is  blackened  right  through,  the 
sulphide  is  washed  off  with  ordinary  water, 
the  result  being  perfectly  transparent  lines 
upon  a  coal-black  ground. 

This  method  produces  a  more  dense  ground 
than  the  bichloride  of  mercury  process  gener- 
ally employed  by  photo-engravers,  and  it  has 
this  advantage  that  the  lines  are  not  easily 
covered.  However,  greater  intensity  for  nega- 
tives from  engravings  and  the  like  will  be 
obtained  by  treating  them  first  with  the  lead 
solution,  then  with  iodide  of  iron  and,  lastly, 
after  a  thoroughly  good  washing,  with  perman- 
ganate of  potash.  The  negatives  assume  by 
this  process  a  deep  brown-black  and  the  lines 
remain  quite  clear. 

This  intensifying  process  is  based  on  the 
following  chemical  actions : 


DEVELOPMENT  IJST  COLLODION  PROCESS.  189 


Potassium  ferricjanide  and  lead  nitrate  form 
lead  ferricyanide — 

K,(Fe,Gju)-^S  Pb(N03)2=Pb3(re,Cy,2} 
6KN0 

Lead  ferricyanide  m  presence  of  silver  con- 
verts it  into  ferrocyanide,  and  being  itself 
transformed  '  to  a  similar  salt  deposits  on  tlie 
former : 

%+2  Pb3(Fe2Cy,,)=Ag,(FeCye)+3  Pb,(reCy,) 

Now  these  two  salts,  silver  and  lead  ferro- 
cyanides  by  being  treated  with  ammonium 
sulph-hydrate  are  decomposed  with  formation 
of  silver  and  lead  sulphites : 

Ag,(reCye)+2  H,S=2  Ag,S+H,(FeCye. 
Pbj(FeC6)+2  H2S=2  PbS+H,(FeCy6). 


CHAPTER  II. 


The  Developer  m  the  Dry  Collodiois 
Process. 


Collodion  dry  plates  are  prepared  either  by 
the  bath  or  emulsion  process.  To  prepare  by 
the  bath  process  the  plate  is  coated  with  a 
bromo-iodized  or,  simbly,  bromized  collodion, 
then  sensitized,  washed  and  flowed  with  a 
preservative — tannin,  gallic  acid,  etc. — which 
plays  the  part  of  a  sensitizer. 

The  latent  image  is  developed  by  a  physical 
or  a  chemical  developer.  If  the  photo  film 
consist  of  silver  bromo-iodide  in  the  proportion 
usually  employed  in  the  wet  process,  4  Nal : 
2  CdBr,  the  image  seldom  acquires  a  sufficient 
general  intensity  for,  as  previously  stated, 
silver  iodide  is  almost  inert  under  the  action 
of  the  latter  (alkaline)  developer.  Therefore, 
in  this  case  the  image  should  be  redeveloped 


DRY  COLLODION  PROCESS. 


191 


after  acidification  to  neutralize  the  alkali  and 
a  tlioroTigli  washing. 

The  development  by  a  physical  developer  is 
preferably  employed  for  transparencies  and 
sometimes  for  bromo-iodized  plates  prepared 
by  the  bath  process.    It  is  as  follows  : 

After  exposure  the  plate  is  wetted  under  the 
tap,  then  flowed  with  a  solution  of,  say,  120 
parts  of  water  and  2  parts  of  an  alcoholic 
solution  of  pyrogallol  at  1 :5,  which  is  allow  1 
to  act  for  one  or  two  minutes,  when  it  is 
poured  off  in  the  developing  cup  and,  a  few 
drops  of  the  following  silver  solution  being 
added,  flowed  back  on  the  film  : 

Silver  nitrate    .     .     .    120  parts. 
Citric  acid  .      .      .      .     GO  «« 

Water  480  " 

In  a  few  seonds  the  image  commences  to 
appear,  and  when  the  details  in  the  shadows 
are  well  out,  more  of  the  silver  solution  is 
added  to  obtain  intensity. 

Starting  the  development  with  much  silver 
nitrate  is  always  injurious.  The  high  lights 
acquire  too  much  intensity  before  the  details 
are  sufficiently  developed. 

The  chemical  or  alkaline  development  of 


192  THE  PHO  TO  GRAPHIC  IMA  GE. 


collodion  dry  plates  is,  of  course,  conducted 
as  in  the  gelatine  process.  We  will,  liowever, 
give  an  example,  observing  that  the  bromide  is 
not  only  useful  to  control  the  development,  as 
first  pointed  out  by  Major  C.  Kussell,  but  also 
to  prevent  fogging.  In  the  dry  collodion  pro- 
cess it  is  a  sine  qua  non,  for  the  nitro-cellulose 
film  does  not,  as  gelatine,  acts  as  a  restrainer. 


A.  Ammonium  seequicarbonate,     50  parts. 
Water   480  " 

B.  Potassium  bromide  ...     10  parts. 
Water    .      .     .      .      .     .  480  " 

C.  Pyrogallol  25  parts. 

Water   480  *' 

D.  Aqueous  ammonia  cone.      .     50  parts. 
Potassium  bromide       .     .     10  " 
Water   480 


To  develop,  immerse  for  a  minute  the  plate 
in  alcohol  diluted  with  two  or  three  volumes 
of  water,  then  in  water  until  the  liquid  is  no 
more  repelled.  Now  take  3  parts  of  A,  1  part 
each  of  B  and  C  and  dilute  with  12  parts  of 
water  ;  flow  this  mixture  on  plate  well  drained: 
if  the  image  gradually  appears  in  all  its  details, 
let  the  action  proceed  until  the  latter  are  well 


DRY  COLLODION  PROCESS. 


193 


out  and,  if  then  the  image  does  not  become 
sufficiently  intense,  increase  the  dose  of  A  and 
C.  When,  on  the  first  application  of  the 
developer  the  image  does  not  appear  within 
20  or  25  seconds,  add  from  1  to  2  parts  of  A. 
Should  the  details  hang  back — the  exposure- 
time  being  then  most  likely  short — add  a  very 
small  quantity  of  D. 

On  the  other  hand  when  the  image  flashes 
out,  either  wash  the  plate  immediately  and  pro- 
ceed to  develop  with  a  solution  containing 
less  alkali  and  more  pyrogallol  and  bromide, 
or  restrain  by  adding  more  of  B  to  the  original 
solution. 

Another  method  of  developing,  also  em- 
ployed for  gelatine  plates  is  the  following : 

On  its  removal  from  the  holder  the  plate  is 
immersed  in  a  solution  of  pyrogallol  and,  for 
collodion  dry  plates,  of  a  small  quantity  of 
potassium  bromide,  say — 

Pyrogallol  .     .     from  1.5  to     2.  parts, 
Potassium  bromide,  (maximum)     0.5  part, 
Water   480.  parts. 

to  which  can  be  added  a  certain  quantity  of 
sodium  sulphite. 


194  THE  PHOTOGRAPHIC  IMAGE. 


In  this  tlie  film  is  allowed  to  soak  for  one  or 
two  minutes,  wlien  20  parts  of  a  solution  of 
crystallized  sodium  carbonate  saturated  at  15^ 
C.  are  added.  If  the  image  appears  in  a  short 
time,  the  plate  is  well  exposed  and  the  devel- 
opment allowed  to  go  on ;  if  it  hangs  back,  the 
dose  of  sodium  carbonate  is  increased  by  suc- 
cessive additions  of  10  parts  until  the  details 
are  out ;  and  if  then  there  is  any  tendency  that 
the  image  develops  too  uniformly,  one  should 
increase  the  dose  of  pyrogallol  and  that 
of  potassium  bromide.  This  is  a  tentative 
method.  The  operation  can  be  reversed  when 
the  exposure-time  is  short  or  the  subject 
lighted  by  strong  oppositions,  as  before  ex- 
plained. 

Cliches  on  collodion  dry  plates  are  fixed 
with  sodium  thiosulphate  1:8,  not  with  potas- 
sium cyanide  unless  developed  by  the  silver- 
pyrogallol  process. 


CHAPTEE  III. 


The  Development  of  Fereotypes. 


The  ferrotypes,  or  direct  positives  on  collo- 
dion films  are,  in  fact,  weak  negatives,  made 
by  under  exposing  and  under  developing. 
Seen  by  reflection,  the  lights  which  are  formed 
of  metallic  silver  appear  white,  whatever  bo 
the  backing,  and  the  half  lights  being  more  or 
less  transparent  on  account  of  the  thin  layer 
of  reduced  metal,  have  no  other  value  than 
that  of  the  backing  itself,  which  may  be  black, 
brown-black,  &c. 

Developer  No,  1. 
A    Ferrous  sulphate    .      .     50  parts. 
Sugar,  white     .     .      .     15  *' 
Water  480  " 


Lead  nitrate 
Water  . 


18 
480 


Mix,  let  settle  the  precipitate,  filter,  then  acid  acetic 
ficid  No.  8,  40  parts,  alcohol  10  parts. 


196 


THE  PHOTOGRAPHIC  IMAGE. 


This  developer  yields  fine  dead-white  tones. 


Developer  No.  2. 


Ferrous  sulphate 

.  15 

parts. 

Potassium  nitrate  . 

.  10 

(( 

Acetic  acid,  glacial 

.  20 

(( 

Alcohol 

.  20 

(( 

480 

(< 

"This  developer  allows  the  image  to  be 
fairly  visible  before  it  is  thrown  off,  taking  in 
cold  weather  nearly  a  minute  to  bring  out  and 
allowing  the  draperies  to  be  seen."  t 

The  silver  reduction  is  lustreless,  but  not 
quite  as  white  as  with  the  above  developer. 

Some  operators  add  half  a  part  of  nitric 
acid  and  30  parts  of  No.  8  acetic  acid  instead 
of  the  expensive  glacial  acid. 

Developer  No.  3. 


A.  Ferrous  sulphate    .      .  72  parts. 
Water   381 

B.  Barium  nitrate  ...  48  parts. 

Water   384 


Dissolve  in  warm  water,  mix,  filter,  then  add  from  2 
to  4  parts  of  nitric  acid  and  48  parts  of  alcohol. | 


*  P.  C.  D,  1853. 

t  John  Spiller,  1855. 

X  Keith,  1857. 


DE  VEL OPMENT  OF  FERR 0  TYPES.  197 


Mr.  Keith — wliose  pictures  are  remarkably 
good,  recommends  a  strong,  fully  iodized  col- 
lodion containing  bromine^  and  a  silver  bath  at 
8  per  100  acidified  with  acetic  acid  chemically 
pure. 

By  substituting  24  parts  of  No.  8  acetic 
acidt  for  nitric  acid  the  reduction  is  dead- 
white  and  the  developer  acts  with  greater 
energy.  As  prepared  by  Mr.  Keith  it  is  feeble ; 
7  to  8  parts  of  ferrous  sulphate  may  be  added 
in  cold  weather  with  advantage. 

These  developers  are  employed  by  very  few 
ferrotypists  although  giving  better  results 
than  the  following,  generally  recommended  in 
modern  treatises  : 

Ferrous  sulphate    .      .     20  parts. 
Acetic  acid  No.  8    .      .     30  " 
Water  480  " 

We  advise  the  reader  if  he  selects  this 
developer  to  add  2  parts  of  alum  and  a  little 
sugar  candy  to  it. 

Mr.  Victor  Petit  states  (1855)  that  by  adding 

*  That  is,  a  few  drops  of  a  diluted  solution  of  brom- 
hydric  acid. 

t  24  parts  of  alcohol  are  then  sufficient. 


198  THE  PHOTOGRAPHIC  IMAGE. 


to  the  above  solution  1  part  of  pyrogallol, 
clearer  proofs  and  purer  whites  are  obtained. 
For  the  same  purpose  Mr.  E,  M.  Estabrock 
has  recommended  (1878)  a  little  tannin  added 
just  before  developing. 

Developing  formulae  with  sulphuric  acid  to 
prevent  the  oxidation  of  ferrous  sulphate  and 
consequently  the  formation  of  a  basic  ferric 
sulphate  which  precipitates  with  the  silver  and 
impairs  the  eclat  of  the  metal  are  often  given. 
Theoretically  this  is  quite  correct,  but  in  prac- 
tice the  whiteness  of  the  lights  is  thereby 
little,  if  any,  injured,  unless  the  developing 
solution  be  used  over  again,  in  which  case  the 
lights  take  an  ochreous  tint. 

"We  advise  the  reader  to  discard  this  acid;  it 
gives  the  whole  picture  an  inartistic  metallic 
lustre  injurious  to  the  half  tones.  To  prevent 
oxidation  sugar  is  sufiQciently  effective  ;  more- 
over, it  acts  as  a  physical  restrainer  without, 
however,  necessitating  a  longer  exposure. 

Pyrogallol  was  the  first  developer  employed 
in  the  direct  positive  process,  but  soon  super- 


DEVELOPMENT  OF  FERROTYPES.  19d 


ceded  by  ferrous  sulphate  whicli  allows  a 
shorter  exposure  to  bring  out  the  latent  image. 

The  whites  obtained  by  pyrogallol  are  beau- 
tiful— ivory-like  and  quite  lustreless.  It  may 
be  employed  whenever  the  exposure-time  can 
be  a  little  lengthened  without  inconvenience  : 

Pyrogallol  ....       3  parts. 
Nitric  acid  (maximum)        1  part, 

Water  480  parts. 

Alcohol       .      .  quantity  suflQcient. 

To  photograph  by  the  ferrotype  process, 
place  the  model  in  a  soft,  subdued  light.  A 
strong  illumination  produces  too  much  con- 
trasts in  this  more  than  in  any  other  process.* 

Expose  so  that  the  developer  acts  somewhat 
slowly,  causing,  however,  the  details  in  the 
shadows  to  be  visible  within  one  minute. 

Before  developing  place  for  an  instant  the 
plate  on  its  lower  edge  on  blotting  paper 
in  order  that  the  silver  solution  accumulated 
at  the  bottom  of  the  plate  be  absorbed  by  the 
paper. 

*  See  our  work,  **  The  Lighting  in  Photographic 
Studios." 


200 


THE  PHOTOGRAPHIC  IMAGE. 


This  done,  flow  the  developer  with  a  gentle 
sweep  over  the  film  carrying  it  across  and  over 
the  plate ;  there  will  be  always  enough  silver 
nitrate  left  to  develop  the  image,  and  a  cause 
of  strain  will  be  avoided,  and  better  modelling 
obtained  in  the  high  lights. 

When  the  silver  bath  is  too  strong,  or  when 
too  much  silver  solution  remains  on  the  film, 
the  layer  of  metal  deposited  on  the  high  lights 
covers  the  half  tones  before  the  details  in  the 
shadows  are  well  out. 

In  order  to  secure  details,  both  in  the  lights 
and  in  the  shadows,  the  writer  found  that  it 
was  advantageous  to  dip  the  plate,  after  sensi- 
tizing, as  usual,  in  another  silver  bath  at  4  per 
cent.    Many  defects  are  thereby  avoided. 

During  the  development  keep  the  solution 
moving  over  the  film  and  let  the  action  pro- 
ceed until  the  details  in  the  shadows  (or 
draperies)  just  begin  to  he  visible^  when,  at  once 
wash  the  plate  under  the  tap. 

Do  not  use  the  developer  over  again.  It 
necessitates  a  longer  exposure  and  does  not 
yield  as  good  whites  for  the  reason  above 
explained. 

Pictures  which  derelop  rapidly  are  generally 


DEVELOPMENT  OF  FERROTYPES.  201 


slightly  fogged,  flat,  without  brilliancy  ;  they 
are  over  exposed  or  the  developer  is  too 
energetic. 

When  both  the  exposure-time  and  the  devel- 
opment are  correct  and  the  high  li^jhts  still 
deficient  in  half  tones  (not  modelled)  the 
collodion  being  then  too  thick  or  too  bromo- 
iodized  should  be  diluted.  On  the  other  hand, 
if  the  collodion  is  too  thin  the  whites,  being 
then  formed  by  a  thin  deposit  of  silver,  are 
impaired  by  the  backing.  This  is  a  common 
defect. 

As  usual,  short  exposure-times  yield  white 
and  black  images. 

Before  fixing,  the  plate  should  be  carefully 
washed,  for  any  trace  of  ferrous  sulphate  forms 
with  the  fixing  agent  (potassium  cyanide)  a 
blue  precipitate  which  stains  the  picture. 

The  fixing  solution  consists  of — 

Potassium  cyanide  .      .     16  parts. 
Silver  nitrate    .      .      .      2  " 
Water  480  " 


CHAPTER  IV. 


The  Development  of  Bromide  Paper 
Prints. 


On  account  of  its  great  sensitiveness  the  "bro- 
mide paper  is  best  impressed  by  an  artificial 
light  which,  being  nearly  always  of  the  same 
intensity,  permits  one  to  work  in  similar  con- 
ditions of  illumination — a  great  desideratum, 
indeed,  to  regulate  the  exposure-time. 

The  light  from  a  duplex  petroleum  lamp,  or 
that  emitted  by  a  large  size  fish-tail  gas  burner 
reflected  by  a  silvered  parabolic  mirror  answers 
quite  perfectly  to  print  by  contact  or  by  the 
camera. 

The  light  being  selected  one  should  try  at 
what  distance  from  it  the  bromide  paper 
should  be  placed  in  order  to  expose  for  not 
less  than  twenty  seconds.  Eapid  exposure- 
time  is  not  a  sine  gua  non  in  this  process ;  far 


BROMIDE  PAPER  PRINTS.  203 


from  it,  it  is  a  cause  of  frequent  failures,  since 
the  paper  being  coated  with  a  thin  layer  of 
the  sensitive  compound  and,  therefore,  allowing 
but  little  latitude  in  the  time  of  exposure,  the 
least  error  has  a  great  influence  on  the  results, 
while  by  long  exposures  a  few  seconds  more 
or  less  do  not  affect  it  much.  This  is  not 
especial  to  the  process,  but  to  every  other, 
whatever  may  be,  after  all,  the  nature  and 
thickness  of  the  sensitive  compound. 

When  the  cliche  is  of  the  ordinary  general 
intensity,  at  a  distance  of  50  centimetres  an 
exposure  of  about  20  seconds  is  likely  correct 
for  most  of  the  bromide  paper  found  in  the 
American  market ;  then,  as  the  distance  in- 
creases, the  exposure-time  also  increases,  but 
inversely  to  the  square  of  the  distance,  accord- 
ing to  a  well  known  law  of  physics.  Hence,  at 
the  distance  of  one  metre,  it  should  be,  theoret- 
ically, 80  seconds  in  the  case  in  question — 
50'  :  100'  : :  20  :  a;  =  80. 

The  best  developer  in  this  process  is  without 
any  doubt  the  ferrous  oxalate.  Three  stock 
solutions  are  employed : 


m  THE  PHOTOGRAPHIC  IMAGE, 


A.    Neutral  potassium  oxalate     .    160  parts. 
Water,  rain  or  distilled     .     .    480  " 

To  this  solution  oxalic  acid  (about  2  parts) 
should  be  added  until  the  test  paper  indicates 
an  acid  reaction. 

B.  Ferrous  oxalate  ....  160  parts. 
Tartaric  or  citric  acid     .      .  8 

Solution  C   6  '« 

Water   480  « 

C.  Ammonium  chloride  .     .     .    120  parts. 

Water   480  *' 

To  develop,  immerse  the  paper  impressed 
side  upwards  in  water  (rain  or  distilled,  any 
water  free  from  lime)  and  let  it  soak  for  a 
few  minutes  until  it  lies  flat,  then  pour  olff  the 
paper,  prepare  the  developing  solution  by 
mixing  1  part  of  5  to  6  parts  of  A  (not  the 
reverse)  and  flow  it  on  the  paper  so  that  it  be 
covered  at  once  on  its  whole  surface.  If  the 
exposure  is  right,  the  image  gradually  appears 
and  gains  vigor.  When  the  half  tints  in  the 
lights  are  visible  and  the  general  effect  good, 
immediately  pour  off  the  developing  solution 
and  without  washing  or  taking  the  print  out 
from  the  tray,  flow  over  it  a  solution  of — 


BROMIDE  PAPER  PRINTS. 


205 


Citric  acid 


2  parts. 


Water 


480 


This  solution  should  be  twice  renewed  in 
order  to  eliminate  the  iron  salt  which  would 
impair  the  whiteness  of  the  paper,  the  pic- 
ture assuming  in  the  fixing  bath  a  yellowish 
tint.  This  done  and  after  a  thorough  washing 
the  print  is  fixed.  The  image  loses  nothing 
by  fixing ;  it  remains  such  as  it  was  after 
development.  Over  developing  is,  therefore, 
objectionable,  although  the  intensity  may  be 

reduced  by  the  Monckhoven's  process  before 
described. 

The  fixing  bath  should  be  slightly  alkaline. 
It  consists  of — 

Sodium  thiosulphate  (hyposulphite),     80  parts. 

Sodium  carbonate  2  *' 

Water   480  " 

"Washing  after  fixing  should  not  be  done  in' 
running  water,  the  reason  is  evident ;  but,  by 
changing  one  by  one  the  proofs  from  one  tray 
to  another  (filled  with  fresh  water)  every 
fifteen  minutes,  whereby,  in  two  hours,  they 
will  be  sufficiently  washed.  The  last  traces 
of  sodium  thiosulphate  are  eliminated  by  a 


206  THE  PHO TOGRAPHIC  IMA  GE. 


weak  solution  of  eau  de  Javelle  and,  this  done, 
if  there  be  any  persistent  discoloration  in  the 
high  lights,  the  prints  are  immersed  in  a  solu- 
tion of  chrome  alum  acidified  with  citric  acid 
and  then  finally  washed  thoroughly. 

The  development  cannot  be  well  controlled 
with  potassium  bromide  which  causes  the 
prints  to  be  tinged  green  if  employed  in  a 
certain  quantity.  Ammonium  chloride,  an 
energetic  restrainer,  is  not  objectionable  ;  but 
it  tends  to  produce  warm  tones.^  Sodium 
sulphite  acts  as  a  weak  restrainer  and  produces 
black  tones  if  added  to  the  developer  in  the 
very  beginning  of  the  operation. 

Some  authors  advise  one  to  use  the  devel- 
oper over  again,  that  is,  to  develop  several 
prints  in  succession.  More  contrasts  are  thus 
obtained,  but  we  question  whether  better 
results  are,  on  the  whole,  obtained.  Yigor 
and  brilliancy  can  be  obtained  by  developing 

*  According  to  Molteni  various  tones  can  be  obtained 
with  the  same  developer  by  varying  the  time  of  exposure. 
Short  exposure  times  lead  to  obtain  black  tones  and  long 
exposure-times  to  obtain  sepia  tones.  By  diluting  the 
developer  various  tones  may  also  be  produced. 


BROMIDE  PAPER  PRINTS.  207 


with  a  weak  developer — one  compounded  with 
less  ferrous  sulphate,  and  softness  by  using  a 
strong  one,  that  is,  containing  a  larger  dose  of 
ferrous  sulphate. 

Necessarily  weak  developers  are  used  in  case 
of  over  exposure-times  and  vice  versa.  As  to 
sodium  thiosulphate  for  accelerator  when  the 
time  of  exposure  is  short,  we  do  not  advise  to 
employ  it,  it  being  liable  to  produce  fogging. 

To  test  whether  the  exposure-time  is  right, 
one  operates  as  usual  by  the  tentative  method. 
The  reader  knows  in  what  the  method  consists 
— flowing  first  the  print  with  the  solution  of 
potassium  oxalate  A,  then  adding  that  of  ferrous 
sulphate  B  by  degrees. 

The  failures  are  necessarily  similar  to  those 
occurring  in  the  negative  gelatine  process,  and 
traceable  to  the  same  causes. 

Those  especially  pertaining  to  the  process 
are — 

Harsh  images. — Exposure-time  too  short; 
developer  not  containing  enough  ferrous  sul- 
phate (oxalate) ;  the  image  not  fully  developed. 


208  THE  PHOTOGRAPHIC  IMAGE. 


The  picture  too  intense. — Reduce  by  Farmer's 
or  Moncklioven's  process  on  the  remoyal  of 
tlie  proofs  from  the  fixing  bath  and  a  super- 
ficial washing,  just  as  when  reducing  negatives 
or  diapositives. 

Prints  flat ;  tinted  whites  ;  greenish  "blacks, — 
Over  exposure-time;  long  development. 

To  tone  grey. — The  development  not  enough 
pushed;  or,  the  developer  not  enough  re- 
strained. 

The  ivhites  yelloiv. — The  developing  solution 
not  enough  acidified.  The  fixing  bath  acid,  or 
the  clearing  acid  not  well  washed  off  before  fix- 
ing (sulphuration). 

Blistering  is  prevented  by  treating  the  prints 
after  developing  by  a  solution  of  chrome  alum. 

Stains  and  markings  are  removed  by  washing 
them  with  a  very  diluted  solution  of  iodide  of 
cyanogen  prepared  by  dissolving  a  small 
quantity  of  iodine  in  a  solution  of  potassium 
cyanide. 

Proofs  over  developed  or  flat  can  be  treated 
in  the  same  manner  and  thereby  much  im- 
proved. 


BROMIDE  PAPER  PRINTS.  209 


Iodide  of  cyanogen  forms  also  a  good  clear- 
ing solution  for  fogs. 

Iron  stains  are  removed  by  soaking  the 
prints  for  an  hour  in  a  solution  of  citric, 
tartaric  or  oxalic  acid.  Very  pure  whites  are 
thus  obtained. 


Eikonogen  is  the  best  substitute  for  ferrous 
oxalate.  The  developing  solution  keeps  well, 
is  seldom  liable  to  stain  the  paper  yellow  and 
yields  clear  images. 

The  following  compound  works  well : 


A.  Eikonogen 
Sodium  sulphite  . 
Potassium  bromide,  1 
"Water 

B.  Potassium  carbonate 
Water 


10 


16  parts. 
40  " 
5 

480  " 

160  parts. 
480  '* 


For  use,  take  of- 


A 

B 

"Water 


480  parts. 
30  " 
160  " 


Formulas  for  the  development  of  Anthony^s 
bromide  paper : 


210  THE  PHOTOGRAPHIC  IMAGE. 


A.  Distilled  water  ....    1000  parts. 
Potassium  oxalate,  neutral  .     300  *< 
Acetic  acid  (to  redden  the  blue 

litmus  paper)      .     quantity  sufficient. 

B.  Distilled  water   ....    1000  parts 
Ferrous  sulphate,  pure    .      .     400  " 
Sulphuric  acid,  CP...        2  " 

C.  Kain  water  100  parts. 

Potassium  bromide  ...        3  " 

Developing  Solution. 

A      ...     60  parts, 
B      ...     10  " 
C     .     .     .      1  part. 


Formulas  for  developing  Eastman's  bromide 
paper : 

A.     Water   1000  parts, 

Potassium  oxalate,  neutral  .     250  *' 
Sulphuric  acid  (to  redden  the 

test  paper)    .     .    quantity  sufficient. 


Water 

Ferrous  sulphate,  C. 
Citric  acid  . 
Sulphuric  acid  . 


Water  . 

Potassium  bromide 


P. 


100.  parts, 
30. 

2.  *< 
0.5  part. 

100  parts. 
2  " 


Developing  Solution. 

A      ...    100  parts. 
B      ...     15  " 
C      ...      2  '* 


CHAPTER  V. 


Vaenishingt. 


It  is  not  absolutely  necessary  of  varnishing 
the  cliches  on  gelatine,  this  substance  being 
quite  hard  and  resistent.  However,  it  is 
advisable  to  do  so,  not  only  to  preserve  them 
from  the  action  of  dampness  and  prevent 
mouldiness  but  also  to  shelter  the  silver 
image  from  any  atmospheric  influence  which 
may  cause  it  to  fade. 

Varnishing  is  also  a  protection  against  the 
various  accidents  which  may  occur  in  printing. 

Self-drying  alcoholic  varnishes,  that  is,  com- 
pounded with  ammonia  and,  sometimes,  plain 
varnishes,  cannot  be  employed  for  negatives 
intensified  by  mercury,  the  intensifying  com- 
pound being  by  place  dissolved  and  rendering 
the  cliche  too  transparent.    In  this  case  it  is 


212 


THE  PHOTOGRAPHIC  IMAGE. 


advisable  to  use  as  a  varnish  a  solution  of  gum 
arabic : 

Gum  arabic  ...  1  part, 
Water  ....  8  parts. 
Olive  oil      .     .     a  few  drops. 

Gum  arabic  is  also  employed  as  a  sub- 
stratum to  prevent  the  alcoholic  varnish 
permeating  the  film  and  thus  to  increase  the 
transparency  of  the  cliches. 


Alcoholic 

Varnish. 

Sandarnac  . 

2  parts, 

Benzoin 

1  part, 

Shellac,  brown 

.      .     1  " 

Elemi  . 

2  parts, 

Oil  of  lavender 

1  part. 

Alcohol,  95° 

.    35  parts. 

This  varnish  must  be  flowed  onto  the  plate 
slightly  warm,  then  drained  off  and  dried  by 
heat.  It  forms  a  good  surface  to  retouch  upon. 

Aqueous  Varnish. 

White  shellac     .  .  20  parts. 
Aqueous  ammonia, 

cone.  26°  Baume  .  25  " 

Alcohol   .      .      .  .  25  «• 

When  dissolved  add  70  to  80  parts  of  water  and  filter. 


VARNISHING. 


213 


Or— 

Bleached  shellac     .      .     32  parts. 

Borax  8 

Sodium  carbonate  .  .  2  " 
Glycerine  .  ,  .  1  to  2  '* 
Water        .     .     .      .  300 

The  cliche  fixed  and  washed  is  twice  flowed 
over  with  this  varnish,  then  allowed  to  dry 
spontaneously. 


END. 


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iii 


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ARE 


A  Record  of  Photographic  Progress. 

I»rice,  per  copy,  so 
I^lbrary  Hdltion,  oo 

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Contains  five  full-page  illustrations—  ^ 

/  All  E^xquislte  Pboto-Gravure,  by  Ernest  Edwards.  \  y 

1^  I              A  Bromide  I»rliit,  by  the  Eastman  Company.  /  O I 

JJJ  )                          A  Silver  I»rliit,  by  Gustav  Cramer,  of  St.  Louis.  f  10  CO 

CD  /                                      Two  ]IIosstypes,  by  the  Moss  Engraving  Company.  >  — 

00   ]  197  pages  of  Contributed  Matter  consisting  of  articles  on  various  subjects,  by  80  repre-  t  (o' m 

—  /                     sentative  photographic  writers  of  this  country  and  Europe.  ]  ^ 

Contains  eight  (8)  full-page  high-grade  illustrations  ;  and  over  ninety  (90)  original  con- 
tributions, written  expressly  for  its  pages,  by  the  most  eminent 
photographic  writers  of  Europe  and  America. 
THE   ILLUSTRATIONS  COMPRISE: 
A  PliotO'I^ltliosrapli,  showing  an  improved  new  process,  by  the  Photo- 
^    I       Gravure  Company  of  New  York.  1  q 

VW  i  A  Pboto-Copper-Plate  Knsrravlns:  of  a  Pictorial  Landscape  Subject,  I  q  I 
00  '       by  E.  Obernetter,  of  Munich.  )  S 

lY^    I  A  Meisenbacli  of  "The  Old  Stone  Bridge,"  by  Kurtz.  /  -j 

^    ]  A  ^inc  Htchitis:.  from  the  Engraving,  which  is  itself  as  fine  as  an  Engraving,  oq 
by  Stevens  &  Morris.  V  3 

A  Cliarmlnsr  Chilld  Portrait,  by  Crosscup  &  West's  improved  process.  \  q. 
Xliree  mosstypes  of  popular  subjects.  And 

330  PAGES  OF  VALUABLE  INFORMATION. 


Contains  the  Following  Full-Page  Pictorial  Plates 


Xliomas  Kdlson.'    A  Portrait  of  the  Eminent  Electrician.   George  M.  Allen  ft 
&  Co.,  New  York. 

**  Babytioo<l.'>  A  Tinted  Photo-Gravure.  The  Photo-Gravure  Co.  of  New  York.  |U 

"  Putnam's  Kscape.''   A  Collection  of  Historic  Views.  The  Crosscup  &  West  m 

Engraving  Company,  Philadelphia.  X 
"  Southern  Krult.'    An  Orthochromatic  Study.  The  Electro-Light  Engraving  , 

Company,  New  York.  ^ 

•*  At  tlie  Barracks.''  A  copy  of  the  great  Meissonier  picture.  William  Kurtz,  N.Y.  > 

**  Minstrel  Party  at  *Jolin  Brown's  Kort.»  "  Photo-Engraving  Com-  "J 

pany.  New  York.  Mi 

O  /   **Jolin  Brown's  Home  and  Grave."  Lewis  Engraving  Co.,  Boston.  ~ 

/    **  Ofif  Duty."   An  Instantaneous  Study.   William  Kurtz,  New  York.  "3 

j^l  ,    **  Minnehatia  Falls  In  Winter."  Levytype  Company,  Philadelphia,  2; 

00  \    ♦*  Central  Park."   In  the  Menagerie.   I.  M  Van  Ness,  New  York.  iL 
*♦  A  Merry  Xale."   A  Child  Group.   F.  Gutekunst,  Philadelphia. 
'*  Xlie  Van  Rensselaer  Manor  House."    Photo-Electro  Engraving 

Company,  New  York.  W 

**  An  Improvised  Studio."  Electro-Tint  Engraving  Company,  Philadelphia.  Ift 

**  Xke  Bats."  A  "  Flash  "  Light  Photograph  in  Howe's  Cave.  William  Kurtz,  N.Y.  ^ 

A  Raider's  Resort."  Morgan's  Favorite  Rendezvous.  M.Wolf,  Dayton,  Ohio.  » 

**  Group  of  Hsqulmaux."  William  Kurtz,  New  York.  |#S 
**  Biatoms."   Photo-Micrographs.   William  Kurtz,  New  York. 

**  Tropical  l,uxuriance."   A  Scene  in  Florida.   Moss  Engraving  Co.,  N.  Y.  ^ 
**  An  Arctic  Camp."   Moss  Engraving  Company,  New  York.  I 
**  Home  of  Hdg-ar  Allan  Poe."   Moss  Engraving  Company,  New  York.  I 

NEARLY  400  PAGES  OF  READING  MATTER.  / 


iv 


THE 

American  Annual  of  Photography 

and  Photographic  Times  Almanac 

 FOR  1891. — 

LARGER  AND  BETTER  THAN  EVER  BEFORE. 


OYer  Tliirty-six  FULL-PA&E  lUustrations.  Over  One  Hundred  Original  ContriDntions. 

PRICK  XHE  SAMH   AS  VSUAI.. 
In  Paper  Covers,  50  cents.      Library  Edition  (cloth  bound),  $1.00. 

By  Mail,  15  cents  extra. 


SOME  OF  THE  PICTORIAZ,  ILJuTTSTJtATIONS : 

A  Fine  Copper-Plate  Engraving  (Portrait  Study).   By  the  New  York  Photo-Gravure 
Company. 

"Attraction,"  "Temptation,"  "  Satisfaction,"  a  series  of  three  hunting  pictures.  By 

R.  Eickemeyer,  Jr. 
The  Solar  Eclipse  (December  22.  1889^    By  Prof.  S.  W.  Burnham. 

Three  Little  Kittens."    By  William  M.  Browne. 
"The  County  Fair."    By  J.  P.  Davis. 
A  Portrait  of  Prof.  Burnham.    By  Hill  &.  Watkins. 
*'  I  Love  '00,"  ta  charming  child  picture).   By  Franklin  Harper. 

Daguerre  Portraits.   (Nine  portraits  of  J.  L.  M.  Daguerre,  including  one  never  before 

published  ) 

The  Yacht  "  Volunteer,"  Before  the  Wind     By  H.  G.  Peabody. 
Finish  of  Race  Between  Taragon  and  St.  Luke.    By  J.  C.  Hemroent. 
"  Enoch  Arden."    A  Portrait  Study.    By  H.  McMichael. 
"  The  Life  Class."    By  Charles  N.  Parker. 
Portrait  Study.    By  William  Kurtz. 

*•  The  Regatta  "   Two  Yachting  Pictures.   By  A.  Peebles  Smith. 

A    Flash  "  Picture.   (Interior.)   By  Horace  P.  Chandler. 

"  Contentment."    By  Miss  Emilie  V.  Clarkson. 

Old  Mill  on  the  Bronx  River.    By  John  Gardiner. 

"  Sailing  the  High  Seas  Over."    By  Harry  Piatt. 

The  Great  Selkirk  Glacier  Face.    By  Alexander  Henderson. 

"  Lightning."   (Two  Pictures.)   By  W.  N.  Jennings. 

"  Down  in  the  Meadows." 

"  Forest  Shadows  "    By  G.  De  Witt. 

"In  Chautauqua  Woods."    By  "A  Chautauquan." 

Haines  Falls.    By  W.  S.  Waterbury. 

Besides  many  Pictures  throughout  the  Advertising  pages. 

That  Americans  like  the  best  of  everything,  and  when  the  best  costs  the  least 

they  will  buy  it  without  urging. 
The  more  distinctively  American  such  an  article  is,  the  greater  will  be  their 
pride  in  it. 

It  goes  without  saying  that  a  full- jeweled  watch  is  worthy  of  a  good  case,  and 
that  an  Encyclopedia  should  be  bound  in  something  more  durable  than 
paper  covers. 

The  American  Annual  of  Photogrrapliy  is  now  in  world-wide 
favor,  and  commonly  spoken  of  as  an  "  Encyclopedia  of  Photographic 
Progress." 

It  should  be  ordered  with  cloth  binding  (Library  Edition),  as  it  has,  both  in 
bulk  and  importance,  outgrown  paper  covers.  Other  books,  containing  no 
more  pages  or  information,  sell  for  $3.00.  In  attractiveness  they  will  not 
compare  with 

The  Photographic  Times  Annual  for  1891,  which  is  the  most  profusely 
and  handsomely  illustrated  Photographic  Book  ever  published. 


IS 
IT 
NOT 

SOP 


"  It  makes  this  already  valuable  book  simply  invaluable.** 

A  CYCLOPEDIC  INDEX 

TO  THE 

AMERICAN  AfflUAl  OF  PHOTOGRAPHY  AID  PHOTOGRAPHIC  TIMES  ALMANAC 

FOR  189I. 


16  CYCLOPEDIC  INDEX. 


Litmus— A  coloring  matter  derived  from  orcella  tinctoria,  a  lichen.  Its 
blue  color  turns  red  when  in  contact  with  acids.  AlkaUnes  restore 
the  blue  color  again  142. 

Lubricator  348. 

M 

Magnesium — A  metal  of  silvery  white  color,  burns  at  a  comparatively- 
low  temperature  with  extremely  actinic  and  brilliant  light  207. 

Magnesium  Flash  Light  —  Pure  metallic  magnesium  reduced  to  fine 
powder.  When  blown  forcibly  through  an  intensely  hot  flame  is 
instantaneously  consumed  and  produces  a  highly  actinic  light. 
Originally  the  magnesium  powder  was  mixed  with  substances  evolv- 
ing oxygen,  and  when  ignited  produced  a  similar  light  249,  207,  135. 

Manganese— A  metal  of  dusky  white  or  grayish  color,  very  hard  and 
difficult  to  fuse  176. 

Mastic— The  resinous  exudation  of  Pistacia  lentiscus,  growing  on  the 
islands  of  the  Grecian  Archipelago,  North  Africa  and  Arabia.  Yel- 
lowish white  drops  or  tears,  soluble  in  alcohol,  chloroform,  ether  and 
benzole  105. 

Mavall,  S.  E.— a  native  of  Ohio,  dyer  by  trade.  Embraced  daguerreo- 
typing  at  an  early  date.  Established  a  studio  in  Philadelphia,  but 
emigrated  to  England,  where  he  and  his  descendants  are  carrying  on 
a  lucrative  business  to  the  present  day  28. 

Meade. — We  find  the  brothers  Harry  and  Charles  R.  Meade  in  possession 
of  a  Daguerrean  studio  in  Albany,  N.  Y.,  as  early  as  1842.  They 
repaired  to  New  York  city  a  few  years  later  and  had  the  first  elegantly 
and  sumptuously  fitted  up  gallery  at  232  Broadway,  where  their  pro- 
ductions stood  foremost  28. 

Mercury  Chloride,  Mercuric  Chloride,  or  Corrosive  Sublimate. — A 
colorless,  crystalline,  semi-transparent  mass,  of  metallic  taste.  It  is 
soluble  in  water,  alcohol  and  ether,  and  very  poisonous  143. 

Microscope — An  optical  instrument,  consisting  of  a  lens  or  combination 
of  lenses  for  examining  objects  which  are  too  minute  to  be  viewed  by 
the  naked  eye  278,  205, 117,  107,  71. 

Molecular— Belonging  to,  consisting  of  or  residing  in  molecules  59. 

Monckhovkn,  Dr.  D.  von — Of  Ghent,  Belgium.  Born  1834,  died  1882 ; 
was  an  excellent  chemist  and  physicist,  who  devoted  himself  chiefly 
to  the  scientific  side  of  photography    94. 

Monochrome— Of  one  color  265. 

Money  Orders,  International  408. 

Morse,  Prof.  Samuel  F.  B. — American  inventor  of  the  telegraph.  One 
of  the  earliest  experimenters  in  photography,  and  more  successful 
than  others  of  his  contemporaries.  He  remained  an  ardent  admirer 
and  promoter  of  the  art  during  the  whole  of  his  useful  life  28. 

Mount  Without  Cockles  348. 

24   PAOHS   IN  AI^I^. 

PRICE,   TEN  CENTS. 

For  sale  by  all  dealers  in  Photographic  Materials,  or  sent  post-paid  on  receipt  of  price 
by  the  publishers, 

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vi 


TWELVE  PHOTOGRAPHIC  STUDIES. 


SECOND  EDITION. 


A  COLLECTION  OF  PHOTOGBAVURES  FROM  THE  BEST  SEPEESENTATIVB  PHOTOGSAPHIC 
NEGATIVES  BY  LEADING  PHOTOGSAPHIC  AETISTS.   The  Collection  inoludee 


'*  Dawn  and  Sunset"  H.  P.  Robinson 

"Childhood"  H.  McMichael 

**  As  Age  Steals  On  "  J-  F.  Ryder 

♦•A  Portrait  Study"   B.  J.  Falk 

*'  Solid  Comfort"  John  E.  Dumont 

"Ophelia"   H.  P.  Robinson 

'*  No  Barrier"  F.  A.  Jackson 

"ElCapitan"  W  H.Jackson 

"Still  Waters"    J.J.Montgomery 

Surf"   James  F.  Cowee 

*•  A  Horse  Race "  George  Barker 

"  Hi,  Mister,  may  we  have  some  Apples?"  Geo.  B.  Wood 


Printed  on  Japan  Paper,  mounted  on  boards.  Size  ii  x  14,  in  ornamental 
portfolio  envelope.    Price,  $3.00.    Sent  post-paid  on  receipt  of  price. 

THE  SCOVILL  &  ADAMS  COMPANY,  Publishers. 


FIFTY-TWO  PHOTOGRAVURES 

IN  SERIES  OF 

Landscapes^  PortraitSy  Figure  Compositions, 
Groups,  Marines,  Special 

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vii 


OTHER  WORKS 

OF 

H.  P.  ROBINSON. 

Picture  Making  by  Photography. 

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with  Photogravure  Portrait  of  Author,  and 
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raphy. Finely  illustrated.  A  new  Ameri- 
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viii 


Wilson's  PiotograpMc  Publications. 

For  Sale  by  The  Scovill  &  Adams  Company. 


WILSON'S  PHOTOGRAPHIC  MAGAZINE.— A  semi-monthly  magazine 
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years  by  Edward  L.  Wilson,  Ph.D.  Gives  almost  800  pages  of 
practical  information,  with  24  embellishments  and  innumerable  pro- 
cess cuts,  all  of  great  interest  to  every  camera  worker,  during  the 
year.  Issued  first  and  third  Saturdays  of  each  month.  Price,  $5.00 
per  year  ;  $2.50  per  half  year.    Subscriptions  may  begin  an)^  time- 

WILSON'S  QUARTER  CENTURY  IN  PHOTOGRAPH Y.— A  com- 
plete text-book  of  the  art.  Twenty-four  hand-books  in  one  volume, 
upon  ever}  branch  of  Photography  ;  528  pages,  profusely  illustrated, 
with  notes  and  index.    Price,  post-paid,  $4.00. 

WILSON'S  PHOTOGRAPHICS.— "Chautauqua  Edition,"  with  Appen- 
dix. By  Edward  L.  Wilson,  Ph.D.  Eighth  Thousand.  Covers  every 
department.  Altogether  different  from  "Quarter  Century."  Fully 
illustrated,  with  notes  and  index.    Price,  post-paid,  $4.00. 

PHOTO-ENGRAVING,  PHOTO-ETCHING.  AND  PHOTO-LITHO- 
GRAPHY.—By  W.  T.  Wilkinson.  Revised  and  enlarged  by  Ed- 
ward L.  Wilson,  Ph  D.  The  most  practical  work  extant  on  these 
subjects.    (Send  for  detailed  contents  list.)    Price,  post-paid,  $3.00. 

ESSAYS  ON  ART. — Composition,  Light  and  Shade,  and  the  Educa- 
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one.  with  150  illustrations,  lithographed  in  facsimile  from  original 
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THE  BOOK  OF  THE  LANTERN.— By  T„  C.  Hepworth.  The  most 
practical  handbook  to  lantern  work  so  far  issued.  278  pages.  Bound 
in  cloth.    Price,  $2.00,  post-paid. 

PHOTOGRAPHIC  MOSAICS.  — An  annual  record  of  Photographic  pro- 
gress. Edited  by  Edward  L.  Wilson,  Ph  D.  Issued  every  Novem- 
ber ;  now  in  its  twenty-eighth  year.  Universally  acknowledged  to  be 
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ix 


